Selective laser melting (SLM) is distinguished for its characters that using of single component metal powder and complete melting of metal powder compared with selective laser sintering (SLS). So the metallic functional model and parts manufactured by SLM possess of fine microstructure and using properties similar to series production, and makes the direct manufacturing of metallic parts by single or small lot possible. The character of SLM and speciality of aluminium powder radiated by SLM process are briefly introduced. Balling phenomena during solidification of molten metal always take place when laser radiates aluminium powder by SLM, the methods such as optimizing of laser processing parameters and flowing of inert gas to overcome it are introduced. The powder of two aluminium alloys AlSi25 and AlSi10Mg are radiated with laser and the samples are made. The microstructure analysis showed that there is no pore and crack in the cross section, the thin microstructure can be divided into thin particle and overlapping zone, the microstructure in the overlapping zone obviously grew. The tensile test proved that the samples manufactured by SLM is distinguished for its excellent properties compared with the sample made from conventional methods. Functional model from aluminium alloys manufactured by SLM is proposed at last.

The microfluidic polymerase chain reaction (PCR) biochip cycle circuit geometry is analyzed. For the general non-closed loop circuit paradigm, the feasible temperature zone arrangement is determined; for closed loop circuit paradigm, the heat exchange efficiency of several structural forms are described. Then the excimer laser etching on polymethyl methacrylate (PMMA) plate mechanism is studied, with the etching rate curves listing by experiments. For PCR chip microchannel fabrication, the channel shape and the bottom surface roughness are mainly considered. In the approach, mask shape is designed to fit with the channel shape;laser polishing, near threshold energy etching, heat annealing for stress relief are adopted to promote the channel surface quality. For the problem of chip bonding, the hot press solution is utilized at last. The hot press bonding system is constructed, the optimal bonding parameters is acquired by tests. For driving and controlling of the micro continuous flow, a pecise pneumatic syringe pump system is developed. By utilizing the PCR chip and pump system, an experiment is performed and the amplified product of a 170 bp DNA template chain is successfully acquired.

This paper analyses the mechanism of dynamical condensation of the laser molten pool and balling effect. Direct metal laser sintering process was used to carry out series of sintering experiments of Fe powder and Ni45 alloy powder. The result indicated that it was easy to appear warpage deformation and balling effect during direct sintering metal powder, and the formation quality of the parts was bad, though getting multi-layers sintered part by adjust process parameters, the density was low. But by using appropriate process parameters, much densification sintered parts by sintering small grain size Ni45 alloy powder can be obtained, its microstructure was fine and uniform, surface smooth and bonding firmly with substrate.

The dynamics and the conditions of amorphous transitions induced in a GeSb2Te4 system upon a single 108 fs pulse melting were studied by real-time optical microscope measurements. The system has a multilayer structure of 100 nm ZnS-SiO2/35 nm GeSb2Te4 /120 nm ZnS–SiO2/0.6 mm polycarbonate substrate. The amorphization is completed within 2.6 ns. The thickness of the phase change layer plays an important role in controlling the heat flow conditions in the system upon a fs pulse irradiation. The relative thermal process and effects are analyzed. The mechanism of crystalline to amorphous transition triggered by single femtosecond laser pulses is discussed.

In manufacturing industry, especially in aviation manufacturing industry, there are many traditional cleaning methods for decontaminating all kinds of product components before assembling. But along with the restricted requirement of environmental protection, as well as the high accuracy and high efficiency, many existing cleaning technology are not suitable for it. Some new kinds of cleaning technology with environment friendly become available nowadays in ultraprecision machining domain. The laser cleaning technology is one of them. The principle and the method of the laser cleaning technology are introduced, and the application of pulse Nd:YAG laser to clean the contaminated parts is researched. The results of the experiment are discussed. Futhermore, the future of cleaning technology is predicted.

Laser Net Shape Manufacturing (LNSM) of Ti-6Al-4V was investigated. The experiments were carried out in open air with shielding argon gas to prevent the materials from oxidation during laser deposition. It was discovered that power mass ratio (PV/Dm) was a key factor, which influenced both surface finish and microstructure of laser deposited parts. High value of power mass ratio will lead to a deposit with good surface quality and large columnar grain growth. The microstructure analysis showed that it consisted of very fine acicular α and β phases, and very dense metallurgical bonding was obtained. The Ti-6Al-4V components with good surface quality were fabricated through processing parameters optimized, in additional, the content of N and O elements introduced during deposition was very low, which indicated LNSM could fabricate the Ti-6Al-4V components with satisfactory quality in open air.

Laser Net Shape Manufacturing (LNSM) of metal components was investigated. The LNSM system was integrated with on-line monitoring and closed-loop control system through which the process of LNSM was studied. It was found that when the real deposited height was larger than the preset layer thickness, the process could be kept stable automatically. When the real deposited height was smaller than the preset layer thickness, the deposition height became smaller and the process gradually became unstable and the process can not go on finally. The influence of processing parameters on the forming characteristics was systematically investigated by design of experiment. By online adjusting the layer thickness to be equal to the real deposition height through applying closed-loop control algorithm, the transfer function of maximum deposition height was obtained. With the guidance of the transfer functions, metal components of nickel-based superalloy with good shape and surface quality were fabricated.

The temperature measurement system of melt pool produced in the process of laser rapid forming (LRF) is established by using a two-color infrared thermometer. The two methods named as real time tracking measurement and fixed point measurement are employed respectively to obtain the melt pool temperature and the cooling rate (temperature gradient) of the melt pool tail. The influences of LRF process parameters on the melt pool temperature are studied. The results show that with the increase of laser power and powder feeding rate the melt pool temperature rises. And the results just reverse as laser scanning speed increasing. With the number of deposition layer and deposition pass increasing, the LRF process presents characteristic of thermal accumulation effect, which means the melt pool temperature gradually elevates. Meanwhile the cooling rate (temperature gradient) of the melt pool tail takes on reverse trend.

Using a selective laser melting (SLM) machine-dimetal 240, a series of experiments for direct manufacturing of precision metal parts were carried out. Some effect factors on precision deposition layer by layer were studied combining with the experiments. They can be divided into three categories: hardware, software and materials. Hardware factors include the beam quality, power and wavelength of the laser, the focusing performance of the optical system, and the scan speed and the powder delivering precision. Software factors mainly include the designing of the metal parts with CAD software, slicing of the CAD model and scan strategies. Material factors are the composition of the material, the melting point, and the shape and the size of the metal particle. CAD models will be manufactured into metal parts by using metal powders with different composition and particle size layer by layer. The analysis shows the parts are metallurgical bonded entities with density of 100%, dimension precision <0.1 mm and surface roughness of about 30 μm.

Direct laser fabrication (DLF) of metallic materials has been carried out by Nd:YAG all-solid-state laser. The effect of the processing parameters, such as laser power, scanning velocity, and power feeding rate on the final deposition result was investigated. The utmost offset of deposited wall in horizontal orientation was also studied. A mechanical performance comparison of samples made by Nd:YAG laser and CO2 laser was also presented. It was found that the metallic parts made by Nd:YAG laser got well strength than CO2,but both fracture strength are higher than the corresponding values got by the conventional processing methods, as well as they all exhibits as toughness fracture.

Directionally solidified Ni-base superalloys with high volume content of Al, Ti are considered unrepairable by traditional welding methods due to its high crack susceptivity to heat input. By strictly controlling the laser parameters, however, sound deposition layers were achieved free of cracks. It was also characterized by directional solidification which was not affected by heat treatment process. Large amounts of secondary γ′ particles were precipitated during heat treatment which greatly influenced the mechanical performance of the deposited layers. The tensile tests both of room temperature and 900 ℃ indicated that the tensile strength of the deposition layers after heat treatment can reach 80% of the base material and the fracture were ductile. The mechanical performance of the deposition layers can meet practical need of industrial use.

Direct manufacturing of metal parts by selective laser melting (SLM) is a newly rapid prototyping technology. Metal parts with metallurgical bonding, high density approximately 100%, low surface roughness and high dimensional accuracy can be produced by SLM in one step. Selective laser melting of Ti-Ni alloy which has excellent biocompatibility is potential for the fabrication of implants and prostheses. The effects of processing parameters on build up characteristic, surface quality and densification such as laser power, scan speed were studied. Gradient grid structure, mechanism and elimination methods of warping of metal parts are analyzed. Experiment result shows that special scanning strategy can reduce the difference in temperature and eliminate warping. The microstructure analysis result shows that a complete metallurgical bonding is obtained by selective laser melting process, and arborescent crystal and isometric crystal were investigated. The microstructure distribution depends on process parameters such as scan strategies, scan speed and laser power.

In the process of selective laser melting of metal powder layer-by-layer, frequent scanning is carried out by the scanning system，so reasonable selection of the laser scanning path is the main problem of this technique. A scanning path generating algorithm, called “blanking” was proposed in this paper. The implementation process of the algorithm is as follows: First, the scanning lines of each contour are generated, while the contour's shape can be divided into convex polygon and concave polygon, and the generating process of the scanning lines of each contour needs special treatments . In order to decrease the number of repeat calculation, the contours can be divided into a series of simply connected region. Blanking method will be used for the contour's scanning lines to generate scanning lines of the layer by the unit of simply connected region. Afterwards, the output order of the scanning lines in the simply connected region will be optimized by the rule of adjacent, and then the blocked final scanning lines can be obtained. These final scanning lines can be used for rapid prototyping process. Test result indicates that the algorithm has a high versatility, rapid generation of the scanning lines.

Based on the connection of macro-sized (centimeters long) double-walled carbon nanotube (DWNT) strands by bandaging their overlapped ends with DWNT films, the joint was reinforced through a current-assisted laser irradiation method. During the laser process, the structural transformation of the DWNT bundles inside the joint provided C-C bonds between the strands, which increased the strength of the joint. Tensile tests indicated that the joints reinforced by laser had relatively higher tensile strength with a maximum value of 335.6 MPa than that of the original ones (maximum value was 189.5 MPa).

With different laser energy outputs, a series of ZnO nanoparticles were prepared using the method of the pulse laser ablation, which were characterized by transmission electron microscope (TEM) images, photoluminescence spectra and Raman spectra. The results indicated that the size distributions and Raman spectra of ZnO nanoparticles were independent of laser energy outputs; however, with the increase of laser energy output, the photoluminescence spectra (PL) of the nanopaticles exhibited a red-shift because of the agglomeration. Finally, the mechanism of pulse laser ablation for ZnO nanoparticles was also discussed.

Double-walled carbon nanotubes (DWNTs) are irradiated by ultraviolet laser. Scanning electronic microscope, transmission electronic microscope and Raman spectroscopy are used to detect the morphology change in the DWNTs. It was found that carbon onions and Fe particles formed after laser irradiation. The morphology and component of these particles are dependent on the laser energy input. As energy input increased from 100～107 mW·cm-2/mm, carbon onions keep growing, while size of Fe particles firstly grows and then reduces with the turning point at 103 mW·cm-2/mm.

Both the single crystalline Si and Er targets are ablated alternately by XeCl excimer laser (wavelength 308 nm) to fabricate Er-doped amorphous Si films on Si and quartz substrates in the vacuum chamber at the pressure of 2×10-4 Pa, and the concentration of Er-doping can be controlled through laser pulse ratio on both Si and Er targets. The samples are subsequently annealed for 30 min in flowing nitrogen. The scanning electron microscope (SEM) images of the samples indicate that more uniform nc-Si films could be achieved at lower annealing temperature by choosing reasonable Er-doping concentration comparing to un-doped samples; The Raman spectra show that Er-doping is valid for the growing of the nanoparticles, but decreases the crystalline degree of the samples at the same annealing temperature. Higher annealing temperature is needed for crystalline of Er-doped amorphous Si films than the amorphous Si films.

Laser micro-cladding technology is a novel method for circuit fabrication. With this method, electronic paste was disposed and sintered by laser process system to fabricate conductor. With the advantages of highly flexibility, easy design and modification, high efficiency and short cycle time, It can fabricate the conductor with minimum line width of 20 μm, which exceeds the limitation of traditional method. In previous work, the circuit fabrication on ceramic, glass and epoxy resin substrates by laser micro-cladding technology was researched. In this article, the conductor was fabricated on semiconductor (Si) substrate. Its minimum line width was about 30 μm and resistivity was at the same level with block Ag,which can satisfy the industrial requirements. The adhesion between conductor and Si substrate was at the order of MPa, which was equivalent with the traditional printing process. The experimental results also demonstrated that the conductor width increases with laser power density increasing, but decreases with the laser scanning speed. There is an optimal parameter range in laser processing. The heat treatment after laser scanning is benefit for conductor's electric performance and adhesion between conductor and Si substrate.

Thick film thermosensor is firstly fabricated on 96% Al2O3 ceramic substrate successfully by laser micro-cladding thick film paste. The sensors have excellent definition and narrow width (minimum 60 μm) with TCR 2.33×10-3 /℃, time answering time 2.3 s and linearity tolerance <1 ℃. The processing parameters that affects the fabricated sensor performance are studied. The performances about the sensors fabricated by the laser micro-cladding technique are characterized. The experimental results demonstrate that the thermosensors fabricated by laser micro-cladding have excellent performances, which are a little better than those fabricated by the traditional silk screen printing methods.

With the advantages of “direct access” and “low-temperature process”, laser-assisted microprocessing can be used in the fabrication of OEICs to realize the optoelectronic compatibility. The achievements which our team has arrived at in the field of laser-assisted microprocessing are presented in this paper. Firstly, the experimental system has been improved, including the hardware platform's building and improving, and the software's designing, and finally developed into an automatic control system with the computer as the core and with optics, mechanism and electronics incorporated. Thus, the amount of experimental errors caused by human factors is decreased and the superior performance devices are accessible through laser assisted microprocessing. Meanwhile, a substantial theoretical analysis and experiments have been done on temperature, a key parameter of laser assisted microprocessing,which mainly includes the measurement of temperature, the analysis of the regularity for change of temperature and the study of the controlling of temperature. Consequently, the accuracy of laser-assisted microprocessing has been improved and the technology has been used for the planar InGaAs/InP PIN photodiode's fabricating.

The thin film inductors with air core have been fabricated by laser micro-cladding technology. It has been studied systematically that how the change of laser power density affects the line width as well as how the inductive structure affects inductive electronic performance. The experimental results show that increasing the turns, broadening the distance between two center lines and enlarging line width will improve inductance at a different level. With the optimum of the laser processing parameters and the structural parameters, rectangular-spiral inductors are processed with area of 5 mm×5 mm and 9 mm×9 mm, line width of 100 μm and 120 μm, distance between two center lines of 250 μm and 500 μm, circle numbers of 8 and 16, and thickness of 1 μm. For those inductors, the range of inductance is from 240 nH±3 nH to 1.2 μH±3 nH, the inductance per unit area was up to 14.81 nH/ mm2 in the frequency range of 100 kHz to 1 MHz . By this technology, the experimental results demonstrate that the thin film inductors fabricated by optimizing structural parameters have the best performances at the same area and structure.

The factors influencing the welding stability and the procedure parameters affecting the weld shaping in laser welding with filler wire of titanium alloy are investigated experimentally, and the reasonable matching sketch between wire feeding rate and welding speed is obtained. It shows that the melting dropt transition and the focus position have significant influences on laser welding stability, while the procedure parameters such as wire feeding rate and welding speed have important effects on weld shaping. In order to obtain the weld shaping with good quality, it is necessary that wire feeding rate must reasonably match with welding speed.

Welding of 1420 aluminum-lithium alloy has been investigated using a high power YAG Laser. The results show that the threshold for penetration welding of 1420 Al-Li alloy is about 1.2×106 W/cm2, lower than those of the traditional Al alloys. Pores, which are the main welding defects, mainly locate near the bond line. Tensile test shows that the weld near the bond line is the weakest part of the joint.

In the automotive industry, more efforts are put to promote the stability of structure while reducing the weight of the vehicle. The application of laser tailor welded blanks is one of the most successful new technologies to be used. Due to its obvious advantages, laser tailor welded technology is widely used in the structure parts of body-in-white. Laser tailor welded inner doors are applied in the new car models of domestic automobile manufactures because of their obvious weight reducing advantages. The structure of inner doors belongs to the typical cover parts and is very complex in its shape. In this paper, the typical characters of laser tailor welded inner doors are extracted. Finite element analysis model of stamping process for tailor welded inner doors are established. By means of finite element analysis and practical stamping, the behavior of laser tailor welded inner doors in stamping process is studied. Simulation and practical stamping results show that the laser welded seam has the obvious movement for the laser tailor welded inner doors during the stamping process.

Bronze bonded diamond wheel is superior grinding performances. It has to be brought into dressing for grinding before its first use or when reaching the service life criterion. Due to the thermal physical and optical differences between bronze bond and diamond abrasive, suitable pulse power density is selected to remove bonds and protrude thus realizing the selective removal. A heat transfer and gas dynamic model was created to describe single pulsed laser ablation which was occurred in the experiments of dressing bronze-bonded diamond wheel by acoustic-optic Q-switched YAG pulsed laser. The average temperature and thickness of melted layer, ablation velocity and depth by different laser power densities was calculated with numerical method. The model is proved to be correct by contrast with the experiment result.

Through the observation and analysis on the surface formation and the milling test of hard alloy under power-density conditions of high and low pulse lasers, it shows that there exist three modes of material removal mechanism milled by pulse laser, including immediate gasification, ejection after being melted, and ablation of material surface. In the process of pulse laser milling, these three modes coexist but plays a different role under different conditions. In the test, under the condition of a low power-density, the removal mechanism for hard alloy material is primarily ejection; under a high power-density condition, the milling surface of the hard alloy shows some fracture in formation, that is, the ablation as the main mode. In the last part, some applications of pulse laser milling are briefly introduced.

This paper systematically studies the mechanism of evaporation CO2 laser cutting high absorptive nonmetallic material. Based on the cutting front and kerf shape photographed in the experiment, a three-dimensional energy coupling model for evaporative laser cutting nonmetallic material is established through theoretical analysis and the reflective transmission and energy absorption of laser against real bended cutting front and both two walls are analyzed. The front and wall's energy absorption is mainly determined by the first three incident beams, that is two reflections. The multiple reflections from the front will increase the power intensity of the bottom and the multiple reflections from the wall will increase the power intensity from the center to the bottom. Due to the multiple reflections, the power intensity distributes over the total front. Both two walls will have waveguide effects on the incident light which will mutual reflect against both walls and transmit toward the bottom of the cut, that is so-called “wall focusing effect”.

Aiming at the droplet transfer behavior under actions of laser plasma and arc plasma together, the origin and action principle produced the force on droplet are profoundly analyzed according to the theory of gas dynamics and the static force balance. The experimental results indicate that the rejecting force caused by metal vapour prevents the droplet from detaching when the material evaporates at the high power density of laser. On the other hand, the laser plasma from laser-induced keyhole changes the original path of MIG arc plasma, which results in that the current density distribution and flow of conventional MIG arc are varied, and produces a new hybrid electromagnetic force in the CO2 laser-MIG hybrid welding process. As a result, the droplet transfer frequency is decreased, and the welding process becomes unstable. Furthermore, the influence of welding parameters on vaporization-induced recoil force and the hybrid electromagnetic force caused by laser plasma and arc plasma together are also studied, and the mathematical descriptions is deduced by adopting numerical analysis, which consequently analyzes the force mechanism of droplet quantitatively, and discloses the internal relationship between the force state of droplet and welding stability in CO2 laser-MIG hybrid welding process.

Single-spot laser and twin-spot laser welding, with or without wire feeding, of aluminum alloy were carried out. The weld shaping, the thresholds of gap width and spot separation, and the states of porosity in weld with various laser welding procedures were compared, and the influences of twin-spot laser on welding of aluminum alloy were analyzed. It showed that in contrast to single-spot laser welding of aluminum alloy, twin-spot laser welding can improve the weld surface quality, increase the weld width and the thresholds of gap width and spot separation, decrease obviously the large porosities in number, but do not the small porosities. Feeding wire in process of single-spot laser welding of aluminum alloy can improve the weld surface quality, increase the thresholds of gap width and spot separation, but increase large porosities in number. Twin spot laser welding with wire feeding can decrease the large porosities in number.

Plasma is produced in deep penetration laser welding. It influencs the interaction between laser source and workpiece plate according to laser beam absorption, reflection as well as refraction etc. Based on micro-focus high speed photograph, dynamic behavior and size of plasma were studied in different laser power and different flow rate of side assist gas. It is discovered that the plasma is larger and more unstable with the increase of laser power density. And the whole process is more susceptible to LSC(Laser Supported Combustion), even resulting in welding discontinuity. By increasing the flow rate of side-assist gas, LSC is supressed and the size of the plasma becomes smaller. Correspondingly, the penetration is slightly deeper with smaller plasma.

Formation of weld root is an important criterion to evaluate the gap bridging ability and weld quality of hybrid welding in gapped butt welding. Therefore in CO2 laser-MIG hybrid welding of stainless steel with 3 mm thick, the effect of welding parameters such as laser power, arc current, distance of laser to arc, welding speed and gap width influencing root width of weld were investigated. Both laser plasma and arc plasma were also observed by CCD camera. The result indicates that there are four types of penetration status with the variation of welding parameters in CO2 laser-MIG hybrid welding. Fine root formation with “moderate full penetration” status can be acquired with appropriate laser power, arc current, distance of laser to arc and welding speed in certain gap. “Partial penetration” and “unstable penetration” will be produced with smaller laser power, or smaller arc current, quicker welding speed, contrarily it will be “excessive penetration”. Effect of laser power on penetration is not effective for bigger gap width. Effect of distance of laser to arc on plasma and root width of weld has also been discussed.

The heat sources arrangement is very significant for the laser-arc synergetic effects of hybrid welding, but there have been few researches about this. So a detail study of laser-arc hybrid welding process was carried out on the 7 mm mild steel by together a 5 kW CO2 laser with a MAG (metal active gas) welder. The results show that the heat sources arrangement parameters, such as heat sources distance, laser defocused distance, angle of weld torch, etc, have obviously effect on the weld shape, and the good weld shape was obtained only with the appropriate parameter combination. The increment of weld penetration depth caused by heat sources distance is the most, which is 55%, and the effects of wire stick-out and laser defocused distance on the weld depth are also stronger. The weld width is more sensitive to the wire stick-out and the angle of weld torch. The effects of these parameters are achieved by the interaction of three mechanisms: the change of laser-arc plasma interaction, the add state of the two heat sources and the state of the forces on the weld pool.

Based on the thermojunction assignment test, actual thermal cycling curve of welded seam heat-affected zone is obtained. After simplifying high-temperature plasma as dot heat reservoir, heat reservoir of light gauge welding as linear heat reservoir and adopting principle of superposition, mathematical model to laser welding zinc coated high strength steel is established and analyzed, meanwhile theoretical thermal cycling curve of welded seam heat-affected zone is obtained. By contrasting the two results, it demonstrates that thermal cycling mathematical model can explain actual thermal cycling process of deep penetration laser welding. Microscale martensite is existed in welding seam microscopic structure, which indicates that thermal cycling characteristic of laser welding is quick heating and cooling velocity.

Weld formation, especially root weld formation is an important criterion to evaluate weld quality and adaptability in Laser-MIG hybrid butt joint welding. A vision sensing system consisting of an external illumination source, a CCD camera, a trigger circuit with the input of MIG current signal and video grabber is established to study the relation between vision signal and root weld formation. The backside image of molten pool is obtained clearly in real time by setting the camera under the workpiece, and the imaging mechanism is analyzed. The image processing algorithm to detect backside width of molten pool, gap width and the offset of molten pool is developed and the calculated result shows a good precision comparing with the actual root width of weld.

Bead-on-plate and butt welding of AA6063-T6 aluminum alloy plates with a thickness of 5 mm is carried out by applying a 3500 W Slab CO2 laser. The penetration welding threshold is measured, and the influences of welding parameters on the process stability are studied. Meanwhile, the different joint tensile strength and appearances are tested. The results demonstrate that welds with good appearances could be obtained when welding with the appropriate processing parameters. The as-welded joint tensile strength without filler wire is 180.7 MPa, while the tensile strength is 190 MPa when welding by one side with the filler wire of AlSi12 or AlMg4.5MnZr. However, the joint tensile strength increases up to 200.7 MPa when welding by both sides with the filler wire of AlMg4.5MnZr, which is about 90% of the base-metal tensile strength. The main reasons for the lower tensile strength when welding by one side are that the filler metal can not totally enter the bottom of the weld and there are porosities at the root of weld.

Keyhole-induced Porosity formation is a severe problem in partial penetration laser welding. Different from the mechanism of traditionally metallurgical pores (e.g. H2, CO pores), the porosity is mainly caused by instability of capillary keyhole and traditional methods employed to prevent metallurgical pores are ineffective in suppressing keyhole-induced porosity. for partial penetration laser welding of 3～5 mm sheet plates the method and mechanism of porosity prevention by pulse modulation was investigated. The experimental results reveal that pulse modulated laser welding can effectively suppress keyhole-induced porosity formation. The variation of porosity ratio as pulse frequency has regularity, that is, the porosity ratio decreases with increasing pulse frequency under 50 Hz, and remains in low level when pulse frequency lies in a wide range of 50～150 Hz. In addition, the optical signal of plasma was detected in pulse modulated laser welding to explain the mechanism of porosity prevention. The results reveal that the porosity ratio varies well with the standard deviation value of plasma signal, which indicates that the mechanism of porosity suppression lies on the fact that the pulse modulated laser welding under adequate frequency can make keyhole stable.

A novel method, laser welding-brazing is presented to joint Al/Ti dissimilar alloys, in which filler metal is AlSi12 and base metal are Ti-6Al-4V and LF6. With this method, the desirable spatial and temporal temperature distribution can be obtained, and then the shape and quantity of intermetallic compounds can be controlled. In experiments, the process characteristics were investigated with the butted joint, the influence of laser power, gap length, feeding and welding speed, laser irradiation position on the joint appearance, interface behavior and tensile-strength were assessed. The experimental results indicate that the joints with good appearance and high tensile-strength can be achieved with this joining method, although the process requirements are rigorous. The shape and thickness of intermetallic compound layer at different positions in the same joint are various. The joint fracture accrues at the interface between titanium alloy and weld when the heat input is inadequate.

Laser spot welding of aluminum alloy is difficult for its high optical reflection and thermal conductivity. The quality of the spot weld depends strongly on the condition of material surface. In this paper laser spot welding of aluminum alloy with different laser pulse shapes was carried out, and the relationship between the pulse shape and the quality of laser spot welds was investigated. Due to the high reflection of aluminum alloy the enhanced spike pulse shape, which has an initial spike of 1.8 kW laser power was used. The surface metal vaporized and keyhole formed, so the rest of laser power can be absorbed sufficiently. The results show that the repetition of laser spot weld was much better using this enhanced spike pulse shape. The ramp-up pulse shape can help to exclude the surface oxide film and stable the formation of spot weld. In addition, cool-down pulse shape was used to minimize the defects such as crack and porosity in the weld. However the surface crater of spot weld using cool-down pulse shape was obviously deeper than the rectangular pulse shape. At last, saw-like pulse shape, which combine the advantages of cool-down and ramp-up pulse shapes, was used and the quality of spot weld was excellent.

A vision sensing system for CO2 laser cutting is designed. By detecting the images of the sparks jet, the relationship between sparks behavior and optimal cutting speed has been investigated. The characteristic signal under different laser power and slab thickness has been obtained. On the given condition, the optimal cutting speed corresponds to the vertical jet angle, the highest outlet brightness and the maximum pixels of different gray scales.

CO2 laser beam butt welding the bimetal saw made of 50CrNiMoVA high-strength alloy steel and W2Mo9Cr4VCo8 high-speed steel has been completed. The influence of side-play amount between laser beam and weld on weld shaping has been discussed. Weld microstructure, micro-hardness and toughness are analyzed through metallurgical test, micro-hardness test and bending test, meanwhile the influence of heat treatment on weld microstructure, hardness and bending property are discussed. The welds without transition layer which are smooth and no external defects, can be obtained. After 1190 ℃ marquenching and three times 560 ℃ tempering for 2 hours, the bimetal saw has no crack in 90° bending test and its property has achieved to industry level.

High-power laser diode-pumped solid-state lasers are replacing flashlamp-pumped solid-state lasers and are widely used in industries. A laser diode-side-pumped Nd:YAG laser is reported. Output laser power of 360 W and stability of ±1% are obtained though the series-oscillation resonator using two laser diode pump modules. There are totally 30 diode bars used in each module and 5 diode bars are placed around the NdYAG rod. There is a flow tube between the diodes and the NdYAG rod, cooling water flows inside the tube and brings out heat. A flat rear mirror and a flat output coupler are used as laser resonator. The structure and output characteristics of the laser are studied in detail. It is shown that the laser is compact and reliable with high conversion efficiency and long life extension.

Laser cutting technology is one of the most advanced cutting technology in the world, adding to the application of layout software, so that the utilization of steel plate has been greatly improved. For filling the lack of sector-annularity parts' research, this paper puts forward the vertexes radial algorithm of sector-annularity parts drawing lessons from the basic principle of the traditional polygonal vertexes radial algorithm, which solves the cutting stock problem of discretional included angle and discretional radius' sector-annularity parts. At the same time, basing on this algorithm, this paper develops a laser cutting layout system using Visual C++6.0, and makes a lot of layout optimal calculations. The experimental results show that this algorithm not only satisfies the technologic requirements of laser cutting technology, but also improves the utilization of silicon steel plate effectively.

Automatic programming increasingly plays an important role in intelligent numerically controlled (NC) coding and Computer-Aided Manufacturing (CAM), which greatly improves the efficiency and reliability of NC system, and relieves the work loads of programming. A graphic automatic programming system for NC laser processing machine LCM-408 is developed by using ObjectARX in AutoCAD and Visual C++. Laser cutting path is presented with the employment of Polyline, in which vertex and bulge are searched out in turn by iterating all graphic entities. The height and width of the tight bounding box of cutting region are obtained by comparing the minimum point and maximum point of the AcDbExtent of each cutting entity. The cut-in or cut-out curve is automatically added to the beginning and ending of each cutting entity for improving the quality of the cutting edge. The cutting sequence can be modified by user choosing one after another or grouping the cutting entities. G-code is generated from the laser cutting path and verified with static simulation.

A set of laser beam homogenizing system, called crossed double strip integrators has been setup in the light of the thesis. The homogenizing result is achieved using this system for a high power CO2 laser, while there are also some limitations. The causation is analyzed in this paper. In the end, the laser sintering Ta2O5 ceramics experiment is done using the homogenized laser beam, proving sintering techniques is improved.

Thermal effects of high power double-cladding fiber laser severely limit the output power and beam quality. Firstly, temperature distribution in high power double-cladding fiber laser was analyzed by thermal conductive equation. Secondly, temperature distribution was simulated by finite element methods, at different conditions. Results indicate that temperature distribution was hardly affected by thermal conductivity of polymer cladding materials, so, when calculating the heat transfer coefficient of the core, the first and the second cladding can be seen as identical; the temperature distribution was great affected by heat transfer coefficient of cladding surface, increasing the heat transfer coefficient can reduce the thermal effects of fiber laser; the cladding's radius also can affect the temperature distribution. Conclusions are useful for designing kW level fiber laser.

Aim at increasing the quality of textured roller by CO2 laser processing, a new laser beam chopping and modulating device was designed based on the beam expanding and focussing transformation characteristic. The laser radiation was transmitted and reflected to the machining surface alternately using a mechanical chopper, which resulted in efficient preheating or double points texturing effect. The selection of optical parameters for the laser beam modulating was investigated. An example application was discussed. Reasonable focal spot and energy density were gained by adjusting the position of the local beam waist and the off-focus degree. The laser textured roll had uniform roughness and high surface hardness, and the hardened bumps improved the abrasion resistant quality.

A laser image scanning technology basing on JPEG is proposed. Using the High compression ratio of JPEG, it overcome the disadvantage that the laser image scanning basing on BMP need too much memory. After decoding JPEG, It needs digital halftoning befor output image data. A multi-Scale error diffusion algorithmic is proposed to save more information from original image. DSP system can deal with the decoding and digital halftoning more quickly.

Powder was likely to be pressed,rubbed, blocked in the delivery process of superfine powder, so superfine powder atomization mechanism was developed and the basic principle of superfine powder feeder was introduced, then a new type of superfine powder feeder was designed. Performance experiments and distant delivery experiments were performed. It was shown that the adoption of special structured mixer avoided aggregation’s occurrence, enhanced the delivery performance of the superfine powder ; linear relation occurred between powder feed rate and wheel speed; optimum working range of air flux was 3～8 L/min; stability was fine and its delivery error was less than 1.8%; stiffness was proportional to air flux, but it was incerse proportion to nozzle, and its distant delivery ability was good.

According to laser fabrication theory, a new three-dimensional (3D) laser beam coaxial powder feeding system was designed. The effect of technological parameters on laser cladding was analysed, and its function was discussed in industrial application. The results showed that the three-dimensional laser beam coaxial powder feeding system can rotate around vertical axis and can swing horizontal axis; the effect of cladding was in inverse proportion to the swinging angle of head at the certain parameters, then the ideal angle was 0°～45°; three-dimensional laser beam coaxial powder feeding system was used to repair parts especially irregular shape parts, such as crank shaft, screw, vane and so on by focusing powder flow and the function of a djustable focus.

It was inportant in measuring temperature field in laser processing for laser intelligence process. The measurement of temperature field in laser processing by color CCD camera and computer image technology was presented in this paper, and which is focused on the calibration of CCD colorimetric method. BF1400 and BBR1000 standard blackbody furnace and WV-CP474 CCD were used in this method. The images of temperature of blackbody furnace had been taken in step of 100 ℃ from 700 ℃ to 1400 ℃. Special program based on VC++ had been developed to process the images, and the relationship between colorimetric level and temperature had been established. It was shown that a good agreement between testing dada and real data, and it will be a useful method for measurement of temperature field for laser process after developed.

The method of laser molten pool measurement by CCD was proposed. A system of temperature field measurement was developed. Proprietary image processing software was developed. Experiments of laser cladding were carried out. It was shown temperature distribution, size and dynamic process in laser molten pool could be measured. It could be a useful device for laser processing after further developed.

This article concludes the new type laser process system of our research which is used to drill 18000 holes on PCB soft board per minute. The via-holes are often jammed in the traditional PCB techniques. It is not easy to clean printing ink with traditional method. To solve this problem, we developed the laser high-speed PCB drilling system. Through two high-speed scan mirrors exchanging the position, the servo system pushing forward working plate, and the exact location of the response system, compensating the shape-change of PCB soft board under computer control. Measure and locate the PCB board with photo electricity system. In order to improve the speed of drilling, we suggested the scan mirror should be 25 mm×25 mm, divide the PCB into several areas, process individually and one by one. Cooperating the position of scan mirror and working plate, the reference frame transforming of holes would be done by software.

The relation between posture of workpiece and measurement, processing was discussed. A conception of adjustable and integrative working table was put forward. Based on determining the best posture and the algorithm of transformation between different coordinates, some parts of workpieces difficult to process now could be dealt with and the effect of processing was improved as a whole. It’s important and valuable for advancing the efficiency and flexibility of laser manufacturing.

Manufacturing quality was greatly affected by the distribution and characteristic of metal powder flow in laser manufacture processes based laser beam coaxial powder feeding. Based on the metal power flow field, A new image processing algorithm called different-level searching algorithm was developed .The movement of powder flow was recorded by CCD camera, and the digitized array was rapidly analysed by the new digital image processing technology of powder flow field. This algorithm was used to find the two small regions which are most related, and their displacement was divided by the time duration, then the velocity rector of this region was obtained. Processing the whole picture, the velocity rector field of powder flow was obtained.The new algorithms compared with the old algorithm, can save more computing time and can improve analytical efficiency.

The elementary theory of three-dimensional (3D) nondestructively anti-counterfeiting identifiers based on liquid crystal mask was explored and a new technology of creating by laser shock wave was set up, which differs entirely from marking by laser thermal effect. The depth information of 3D identifiers is acted as anti-counterfeiting information, and a new-type and high-efficiency theory of measurement and identification on 3D anti-counterfeiting identifiers by 3D identifiers' reconstruction and binary coding is established originally. The anti-counterfeiting properties 3D identifiers are studied, which is beneficial to design and manufacturing of anti-counterfeiting identifiers.

The characteristic and application of laser shock processing (LSP) was introduced, then the surface profile, surface residual stress and fatigue properties of laser shock processed titanium alloy were studied. The results showed that laser shock processing had obvious effects on titanium alloy. There was shocked zone on the surface of the metal after laser shock processing, which with the same size as laser spot and depression of 10～20 μm, the most residual stress was about -600 MPa, which corresponded to the result with intense shot peening, but the intensity of plastic deformation was much more than that of shot peening. Suitable laser parameters and overlap rate can gain smooth and even surface, there were obvious marks, little deformation and no cracks on the surface of dual beam laser shock processed titanium turbine blade.

NiTi shape memory alloy (NiTi SMA) has been widely used for many medical applications such as dental and orthopaedic implants. Laser gas nitriding is one of the most effective methods to improve the surface performance of NiTi SMA. Laser gas nitrided layer was fabricated on the surface of NiTi SMA after irradiated by a continuous wave Nd:YAG laser in N2 environment. With optimum process parameters, a compact laser modified surface MMC coating reinforced with fine TiN was achieved. There was a layer of TiN ceramics on the top of modification layer, with a thickness of 1～2 μm. Then the amount of TiN reinforcement gradually decreases across the coating. Morphology and composition and biological activities were individually investigated by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), experiment of the immersed in simulated body fluid (SBF) at 37 ℃. The results indicated that there was a good metallurgical bonding between the hard modification layer and the NiTi alloy substrate. Laser gas nitriding can effectively improve the ability of NiTi SMA to induce the formation of bone-like apatite in vitro environment.

Laser cladding of Al-Si+Al2O3 composite layer on ZL102 alloy was performed by 5 kW CO2 laser. The effect of the laser cladding parameters to layer was investigated. The analysis on the microstructure, the hardness and wear resistance of laser cladding layer shows that, the Al-Si+Al2O3 layer is uniform, continuous and free of pores and cracks by optimized parameters. Al2O3 particles disperse in the matrix of α-Al and α-Al+Si eutectics with particle size of 10～20 μm. The interface between the layer and the substructure was epitaxial, with excellent bonding by the strong metallurgical interface. The hardness and wear resistance of laser cladding layer is about 2 times (in the range of Hv 190～260) and 4 times higher than that of the substrate, respectively.

Based on optimum design of composition using the cluster line criterion, the Cu-Zr-Al alloy coating was prepared by laser cladding on the magnesium surface. The result showed the coating consists of amorphous, Cu8Zr3, and Cu10Zr7 phases. Because cooling rate increases and dilution degree decreases with increasing of scanning velocity, the content of the amorphous phase in the coating increasesed, its maximum reaches about 61%. At the meantime, the hardness, Young's modulus, and wear resistance of the coating decrease due to reducing of intermetallics enhancement, while the corrosion resistance increases.

Pure titanium and titanium alloys are the optimum replacement materials for the surgical implants. Laser surface modification is an attractive method to enhance the surface hardness and wear and corrosion resistance of titanium alloys. In the present study, the investigation into laser gas nitriding processing of the Ti6Al4V alloy can be used 2 kW continuous wave Nd:YAG laser under an N2 environment. With optimum process parameters, a compact laser modified coating was achieved, free of crack and porosity. The percentage composition of pernicious elements Al and V in the nitriding coating surface is very low. Morphology and composition and the frictional wear and electrochemical corrosion activities in Hank’s simulated body fluid at 37 ℃ were individually investigated by using SEM, EDX, ball-on-disc tribometer and anodic polarization measurements. The results indicated that the wear resistance and electrochemical corrosion behavior are improved significantly by laser gas nitriding without changing the property of the Ti6Al4V substrate used as biomaterial.

Friction and wear comparison tests of laser hardening and medium frequency induction hardening were performed using friction wear testing machine. And the microstructure of hardened layer was characterized by SEM, TEM and X-ray Diffractometer. The test results show that the wear resistance of laser hardening is 4%～21% higher than that of medium frequency induction hardening under the load of 50～250 N. However, the friction coefficient of laser hardened specimens is lower than that of medium frequency induction hardened ones. The frictional behaviour of them is grain abrasion. But the width and the depth of wear trace treated by medium frequency induction hardening were greater than it treated by laser hardening. The microstructures of hardened layer are lath martensite and less acicular martensite. But more carbide was been precipitated in hardened layer treated by medium frequency induction. And more residual austenite was leaved in it.

Through control technological parameter of Nd:YAG pulse laser, current, pulse width, frequency, spot diameter, scanning velocity and defocusing, laser surface cladding Al-Y(1.4%) was used to repair corrosive damage of aluminum alloys. One group of the specimens was shocked on every cladding layer. After aging and fatigue test, crack pattern and microstructure were analyzed. The result showed that the fatigue life of the shocked specimens was much longer than the specimens’ without shock. The crack pattern of the shocked appeared fatigue strip, the microstructure showed there was no obvious pore and crack in the cladding layer which was metallurgy combination with the substrate.

The processing characterizations and the sintering effects of laser sintering were researched and presented with the tests of different functional ceramics, such as Ta2O5, Al2O3, BaTiO3, Na0.5K0.5NbO3 (NKN). It is shown that the temperature field consisting of homogenized temperature along the radial and proper temperature gradient along the axes of the ceramics is the key point for sintering. As a rule, the laser power for sintering high melting point (2000 ℃) ceramics is up to 103～104 W/cm2. The absorptivity of materials for a certain value of wavelength, the material of sample stands and the power adjustment curve should also be concerned. The special structural and morphological properties of the non-equilibrium high temperature phase, grain-oriented microstructure and high density in the laser-sintered ceramics were also shown. As a progressive and effective means for preparation of functional ceramics, laser sintering technique has been shown be worthy of extensive investigation.

Al-Ti-C refining master alloys, reaction among whose composing elements are exothermic, are fabricated by laser induced self-propagating high-temperature synthesis. Results show that TiC particles average size is less than 1 μm and distributes dispersedly and TiAl3 is strip-like in Al-50(TiC) master alloys. The master alloys have excelent refining efect on pure aluminium. The aluminium grain average size decreases to less than 150 μm after adding 0.1% the master alloys which have good resist-decline ability. There are a sharp endothermal peak and a obtuse exothermic peak on the differential scanning calorimetry (DSC) curve. The reaction process of self-propagating high-temperature synthesizing the master alloys is analyzed.

By means of laser cladding process a Ti-functionally graded material (FGM) was successfully obtained based on Ti600 with preplaced powder mixtures of Ti, ceramic material and nickel based alloy powder. The wear properties of Ti-FGM presented a graded distribution. It was revealed that with a proper ratio of the mixed powder and laser cladding processing parameters, the Ti-FGM which reinforced by in situ formed TiC particles can be obtained. Light optical microscopy (LOM) and scanning electron microscopy (SEM) were used for analysis of microstructure. The results showed that, a functional graded material was successfully fabricated by laser cladding, TiC particles can be formed by in situ reaction of titanium and ceramic material. The first coating had good metallurgical bonding with the substrate. The coatings were continuous, homogeneous and crack-less with optimizing the technical parameters, and had no borderline.

Laser cladding of powder mixture containing titanium, aluminum, niobium, chromium, carbon and other elements have been conducted on Ti-6Al-4V substrate in order to synthesize titanium aluminides matrix composite coatings reinforced by in-situ titanium carbide particles. Primary analysis of morphology, microstructure, composition, phase structure and microhardness of the coatings had been performed. The results revealed that the microstructure of coatings obtained here can be characterized as γ-TiAl grains+γ-TiAl/α2-Ti3Al lamellas+carbide particles. The γ-TiAl grains exhibit equivalent diameter of approximately one micron. The even distance of lamellas is below 500 nm. The carbide particles exhibit a stick length of several microns and distribute uniformly throughout the coating.

To improve the wear-resisting property of TC4,an experiment of laser cladding (Ti+ Al/Ni)/(Cr2O3+CeO2) on titanium alloy by pulsed Nd:YAG had been carried out. The effects of processing parameters on the cladding layer height, dilution rate and penetration into the substrate had been examined. Microstructure of the layer was investigated, and microhardness was measured. It was found that both the clad height and penetration into the substrate increased with the increasing pulse energy. The dilution rate reached the lowest value (3.95%) at the incident energy of 20 J/pulse, pulse width of 8ms,the scanning speed of 1.1mm/s and pulse frequency of 5 Hz. The microstructures of the cladding layer were dispersive undissolved Cr2O3 particles and orbed liquid-precipitated Cr2O3 distributed in the matrix consisting of fir-tree crystals and eutectics. And the ceramic hardening particles of TiAl was existed. The hardness of the cladding layer increased obviously, the maximum was 1150 Hv,2～3 times of the substrate. A white narrow metallurgical bonding zone was formatted at interface between the clad and the substrate, about 10～20 μm. The cladding layer was continuous, homogeneous, poreless and crackless by optimizing the technical parameters.

Adding carbide-formation elements into the high-carbon-equivalent FeCSiB molten pool induced by laser cladding or laser alloying is favorable of the formation of high wearable metal matrix composite coating with multiple carbide particles reinforcement by in-situ synthesizing and with strong metallurgical bond to the substrates. They play different roles in promoting the nucleation and growth of the reinforcement carbides, among which Ti is the most important element for particle nucleation. The adding combination of the strong carbide formation element (Ti+Zr+Mo+WC) was optimized. Tribological tests and application checks in typical key parts approve that the laser produced composite coatings reinforced by in-situ particles demonstrated excellent wear resistance and coupling capability. The above concept on producing in-situ synthesized particles reinforced composite coatings has been successfully used in laser surface strengthening of nickel-base alloy.

In this paper No.45 steel (equivalent to AISI 1045) was laser alloyed with a special laser alloying powder TH-2. With SEM in situ observation of crack growth from base to alloying zone, the relationship between FCGR and stress intensity factor range (SIFR) was investigated, and the structure morphology of surface crack path and the fatigue fracture was analyzed. It is found that crack would appear on laser alloying zone (LAZ) after a certain cycles, but the boundary of LAZ would retard crack growth. Unstably propagation would occur when the crack from base meet the crack on LAZ. The relationship between FCGR and SIFR was not agreed with Paris formula. Typical fatigue strips was found on fatigue fracture of base and the morphology of LAZ was brittle fracture. It was necessary to design special alloying powder for different base material. To increase ductile phase in LAZ would improve resistance to fatigue crack growth of LAZ.

The experiments of laser-clad nickel-based alloy powder doped with (MoO3+B2O3) were carried out on steel A3 substrate. The microstructural and metallographic analyses were performed by a scanning electron microscopy, energy-dispersive spectrometer and X-ray diffractometer. Effect of content of (MoO3+B2O3)-doping on the cracking susceptibility and the microstructure of Ni-based composite coatings has been analysed. The hardness and wear-resistance of the coatings were also studied. It is shown that good finish and crack- and porosity-free coatings can be achieved under a proper amount of (MoO3+B2O3)-doping and a suitable processing technique, and that a strong metallurgical bonding is presented between the coating and the substrate. Both the cracking sensitivity and the wear resistance are considerably improved at the little expense of a decrease in hardness. This can be attributed to the refinement of the microstructure both in grain sizes and their homogeneous distribution in the coatings. The microstructural and metallographic analyses suggest the composite coating consists of the eutectic composed of BMo2C, Cr23C6 and Ni4B3 dispersed in the γ(Cr-Ni-Fe-C) matrix. Thus, it can be concluded that the refinement in microstructure is due to both an increase in number of nucleation sites by the formation of BMo2C in the melting pool and an impediment to the growth of larger brittleness phase CrB by the (MoO3+B2O3)-doping.

Spot array laser alloying of C-Si-B-RE on nodular cast iron using CO2 laser has been made. The microstructure and characteristics of the alloying layer and HAZ have been analyzed and thermal fatigue tests on the laser treated samples have been done. The results demonstrate that laser alloying of C-Si-B-RE on nodular cast iron is able to achieve satisfying layers with high hardness and smooth surface which are free of cracks. The laser treated specimens were tested under the specified thermo-cyclic condition: 700 ℃～25 ℃, heating 90 s, cooling 10 s, 90 times. The results show that the initiation of the crack in the substrate is relevant to graphite nodular and its morphology. The thermal fatigue cracks in substrate and alloying area are retarded by the HAZ. The initiation of the crack in the HAZ is relevant to the oxide formed during thermal fatigue test. The refining pearlite colonies in heat affected zone (HAZ) compel the crack to develop slowly along the grain boundaries.

The pulsed Nd:YAG laser cladding is one of the most effective methods of the precise repairing technology. It is decided by the voltage, electric current, pulse length, pulse frequency, scanning speed and beam diameter of the Nd:YAG laser. In order to fully consider the effect of these processing parameters and simply the adjustment processing parameters, spot overlap rate definition is referred. And the calculation equation of spot overlap rate is formulated. The experiment was carried out with precoated layer and wire feeding laser cladding repairing. The clad layers are found perfectly at single pulsed energy of 6.7 J and spot overlap rate of 97.4%. Different kinds of defects produced by wire feeding laser cladding are observed by SEM. The reasons of producing defects are preliminarily probed.

A new technology-controlled laser shock peening which is applied by using a high energy pulsed laser to induce a high amplitude shock wave to make surface modified is introduced. It can improve fatigue life, corrosion and wear resistance of metal part. The fatigue life and the corrosion resistance do not always increase with laser shock peening intensity linealy. Optimal fatigue life and corrosion resistance depend on magnitude and distribution of residual compressive stress, and influence by optimization of various laser processing parameters. Laser processing parameters have a crucial effect on residual stress. Selecting laser processing parameters according to preconcerted fatigue life and corrosion resistance becomes a present subject. Laser shock peening mechanism has a significant relation with the generation of residual stress. In this work, the effect of laser processing parameters such as laser power density, laser beam diameter, laser pulse width on distribution of residual stress, and the relationship between these parameters and residual stress depth are examined. Specimens of QT700-2 are used in this investigation. The magnitude and distribution of the residual stress are measured by using an automatic X-ray diffraction technique. It is observed that while residual compressive stress induced by laser shock peening reach an optimal level, the surface of metal part can obtain optimal fatigue life and corrosion resistance, then optimal combination of laser processing parameters can also be obtained.

The high power density, Nd:Glass laser shocking system with five-axes NC worktable was used to shock the fillet of main and rod surface of crankshafts. In the experiment, the parameters of laser shock processing are as follow: laser wavelength was 1.06 μm, pulse duration was 23 ns and output power ranged from 25～40 J. Flowing water and the ethyl silicate materials was used as confinement layer and absorbing medium respectively. Residual stress, hardness and wearability of the laser shocked surface were investigated as functions of laser processing parameters. The results show that the shocked zone has no obvious macro deformation,but the hardness and compressive stress of the laser processed surface was significantly enhanced,the wearability was increased about 1.4 times compared with those without LSP, which is favorable for the fatigue properties of crankshafts.

The value and distributing form of the residual stress in laser peening forming (LPF) decide the final sheet contour and deformation shape. To accurately control the distributing of the residual stress and shape the sheet in desiration, it was significant to invest the distributing form among single peen, multiply peen in the same spot and different spots. The experiment of 2mm thick AL6061-T6 and LY12CZ sheet with thickness of 1.2mm was carried out with Nd:Glass high power pulsed laser. The residual stress of peened target was measured by the X-350A stress analytical facilities. The influence of process parameters, such as laser energy, sheet size, peenning path to the residual stress distributing was investigated deeply. The mathematical modeling of shock wave load based on laser peening was established, and a finite-element analysis method based on the ANSYS/LS-DYNA software is applied to simulate the sheet deformation process.

A laser cladding process monitoring system was set up based on CCD camera, dynamic behavior of melt pool can be acquired as a video form through the system. The melt pool's digital image is read from the video frame by frame and the steady melt pool area can be obtained. A kind of algorithm was studied and implemented. This algorithm can get the clear melt pool's contour and centroid. Jointed each pool's centroid of the single pass, a relative height curve is formed, and it can approximately describe the deposition's surface. On the basic of the communication between the image collection card and the computer image process cell, a realtime consecutive image process software was developed. The software can accomplish the image collection and process within 0.2 s. These are monitoring elements for finding the actual melt pool position and further laser cladding process close-loop control.

Theory analyze the creep property of film in fluctuating temperature conditions. A numeric model is established basing on ANSYS software with taking WC-6%Co as substrate and (Ti,Al)N as film. The degradation rule of temperature field and stress field with the increasing and decreasing film's temperature are analyzed. The calculated results show that: in the fluctuating temperature conditions, the function of stress creep can be derivated by the one of stress creep curve under the history temperature of constant temperature. And the compress stress increases with the increasing of temperature, the tensile stress is produced with the decreasing of temperature. The size of tensile stress in the direction of normal axis is three times as big as optical axis. The fracture of film probably happens more than that of spall.

On the basis of the principle of laser-peening (LP) and shot-peening (SP), the finite element method (FEM) model of LP and SP are established based on the software ABAQUS. To LP, the switchover loading of laser shock wave is solved; To SP, the assemble between pills and sheet metal is settled. The residual stress in the thickness after one LP and multi-LP and the distribution of residual stress after single pill and multi-pills shot the sheet metal are analyzed. The depth, magnitude of residual stress, the quality of surface and the shape of surface after the LP and SP are compared, respectively. The conclusion is that the effect of improving the employing longevity after LP is better than SP’, the LP technique is and will be substitute for the SP technique to change the property of material and widely be used in manufacture.

In order to control forming accuracy of laser cladding thin-wall metal parts, on the basis of analyzing technology theory and affecting factors of metal parts wall thickness in laser cladding, a nonlinear mapping between wall thickness of metal parts and laser power, spot diameter, scanning speed, powder feed rate is established by using BP artificial neural network. By using momentum coefficient, adaptive learn rates and optimized weights and bias, the problem of BP that easily falls into local minimum point is overcome. Experimental parameters are chosen as training samples, and BP neutral network is trained. Experimental and simulated results show that the maximum relative error of training and testing samples are 1.93% and 1.19% respectively. The optimized BP neutral network model can be used to process parameter optimization and predict forming accuracy of laser cladding metal thin-walled component for on-line control system.

Laser shock processing (LSP) is a novel surface treatment technology which uses laser-induced shock wave to strengthen material surface. The magnitude of the surface residual stress and the depth of compressive residual stress are important indexes for the evaluation of LSP's effect. The finite element method (FEM) simulation is a valid means for predicting residual stress field distribution in the metal after LSP. The ABAQUS software is applied to simulate the laser shock processing of 6061-T6 aluminum alloy. It discusses how to deal with finite element model, material behavior, the loading of laser shock wave, solution time and so on during the FEM of LSP, and the distributions of residual stress field induced by shock wave are also analyzed. At last the effects of multiple LSP processes on the residual stress field were evaluated by using FEM.

The ZrW2O8 ceramic was successfully synthesized by laser sintering for the first time in this work. The microstructure observation by a scanning electron microscope shows that crystalline grains of the ZrW2O8 ceramic samples are fine and homogenous and that their size is about 10 nm. The analyses by an X-ray diffractometer and Raman spectrometer exhibit that only α-ZrW2O8 exists on the outside but both α-ZrW2O8 and γ-ZrW2O8 exist in the bulk of the sample. It is also confident of that ZrW2O8 ceramics can be effectively synthesize by laser sintering. The existence of γ-ZrW2O8 in the bulk may be due to the huge stress generated in the laser sintering processing. Moreover, the effect of laser scanning velocity on the properties of ZrW2O8 ceramic was analyzed. It is indicated that the amount of γ-ZrW2O8 in the bulk could be effectively cut down by means of appropriately reducing scanning velocity and optimum laser power density.

A numerical simulation was studied on field of temperature in ceramics by using FDM (Finite Differential Method) during the laser sintering. At first, the heat conduction equations were given, then the boundary condition was given, Finally, the mathematical model of the laser sintering on ceramics was given and the equations were solved by FDM. The simulation program was given by above method, and then the change of field of temperature in ceramics was described by simulation program. The effect of technological conditions on field of temperature in ceramics was analyzed. It shows that the lengthways temperature gradient in ceramics is only relevant to the laser power, and the transverse temperature gradient in ceramics is relevant to the laser speckle radius and the transverse intensity distribution of laser.

A good finish and compact Al2(WO4)3 ceramic had been successfully and rapidly synthesized with a proper proportion of Al2O3 and WO3 by laser sintering. The microstructure observation, component and phases analysis of this ceramic were performed by a Raman spectrometer, scanning electron microscopy, energy-dispersive spectrometer, thermal analyzer and X-ray diffractometer. The Raman spectrum revealed that the volatility of WO3 can be avoided in the laser sintering and that the raw materials can react completely under suitable processing parameters. The analysis by a X-ray diffractiometer indicated that the sample of Al2(WO4)3 with orthorhombic structure, belonging to space group Pnca, was comparatively pure but included a small quantity of AlxWO3 (x≤1) and WO3-x (x<1). The investigation by a scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) showed that the ceramic was composed of small crystal conglomeration in which the stoichiometric proportion of elements was almost identical. The thermal analysis reveals that the impurities in the Al2(WO4)3 ceramic was various remaining non-equilibrium phase.

The study on laser sintering of Ba(Ti0.95Zr0.05)O3 (BZT) piezoelectric ceramics was introduced. At first, the powder of BZT was prepared by traditional ways. The green patch was sintered by the CO2 laser which the largest powder was 150W and the rotate speed was 1440 rad/min and the time was 10 min. The piezoelectric ceramics character of BZT ceramic was showed through measuring the dielectric constant-temperature and impedance-frequency data. The ceramic sample by laser sintering had higher courier temperature through comparing the dielectric constant-temperature of two ways which are traditional ways and laser sintering. It was found that ε=1563, d33=45 pC/N. The data of XRD showed that the two peak values ［(111), (002)］ had been enlarged and it was observed that the crystal grain had grew in the ceramic. The measure of laser sintering could be regarded as one of the ways to sinter the functional ceramics.

Molybdate and tungstate were synthesized by the standard solid state reaction technique or co-precipitate method traditionally. But all above-mentioned methods have some unavoidable disadvantages, such as complicated technics, longer time, uncompletely production, so that can not apply to industry. A novel synthesis technology by laser sintering is given in this paper and it could overcome the above-mentioned shortcoming effectively. The sample of La2(MoO4)3 had been synthesized using this new fabricating method for the first time. It is shown that sample of La2(MoO4)3 possesses compact structure and good figure. The analyses by a Raman spectrometer and X-ray diffractiometer reveal that the raw material reacted completely and the sample is the same structure. The investigation of the specimen surface by a scanning electron microscope and energy-dispersive spectrometer shows that the surface is composed of small crystal conglomeration in which the stoichiometric proportion of elements is the same.

Epitaxial thin films of La0.67Ba0.33MnO3 was grown on the LaAlO3 (001) substrates using pulsed laser deposition (PLD). The thickness dependence of magnetotransport properties close correlated with the strain effect was studied. The out-of-plane lattice parameters dependence on variable thin films thickness was analyzed in detail by X-ray diffraction (XRD) data. In contrast with usual results that compressive strain enhances TC by increasing the transfer integral t0, compressive strain due to mismatch between LaAlO3 substrate and La0.67Ba0.33MnO3 film was found to suppress ferromagnetism and reduce TC. The anomalous magnetotransport of La0.67Ba0.33MnO3 thin films was explained by strain effect of colossal magnetoresistance (CMR) materials on the stability of eg orbital.

When the poly vinylidene fluoride (PVDF) disk is irradiated by the laser with wavelength of 248 nm, the surface electrical conductivity of the sample is increased nine orders of magnitude to 10-4 (Ω·cm)-1 and the electrical conductivity of initial sample before laser irradiation is 10-13 (Ω·cm)-1. With adjusting the laser energy density, the gas atmosphere, the pulse frequency and the number of laser shots, the optimal technological conditions of the laser irradiation was obtained. Based upon the analysis of X-ray diffraction, Raman spectroscopy and micrographs of the samples, we conclude that laser breaks the C-F bond leaving graphite on the surface of the samples which lead to the transition from an insulator to a conductor.