Nano manufacturing technologies attract global attention and research, among which laser nano manufacturing is a key focus. Starting with the introduction of laser far-field nano-manufacturing technologies and especially near-field nano-manufacturing techniques for fabrication of surface nano structures and 3D nano structures/devices, the summarizing of emerging applications of these technologies is focused on, including metamaterials, photonic crystals, data storage, biomedical applications, sensors and functional surfaces. The detail summary of the emerging applications of nano-manufacturing technologies is aimed at stimulating the research and development of laser nano manufacturing technologies.

The recent progresses of fiber sensor fabrication in our group are reviewed. Novel inline fiber Mach-Zehnder interferometer (MZI) sensors with various structures are proposed and manufactured by femtosecond laser fabrication and fusion splicing for high-quality sensing of refractivity-sensitive parameters such as temperature, concentration, humidity, pressure, stress and strain: a) for an MZI sensor with a trench on a single-mode fiber, the refractive index (RI) sensitivity of acetone vapor is about 104 nm/RIU (refractive index unit) and the temperature sensitivity is 51.5 pm/℃ from 200 to 875 ℃; b) For an MZI consisting of two micro-air-cavities, the sensitivity is 501.5 nm/RIU and the detection limit is 1.994×10-6 RIU at the refractive index of 1.4; c) to reduce the fabrication cost, a new fusion-splicing based method is proposed to fabricate MZI sensors; the sensitivity is 664.57 nm/RIU with a detection limit of 1.5×10-6 RIU and its cost is tens of times cheaper than those of commercialized long period fiber Gratings; Also, 5×10-5 acetone vapors are successfully detected by the MZI sensors coated with zeolite thin films.

Micro-scale laser shot peening (μLSP) is proposed as a new technology using shock wave pressure generated by the interaction between micro-scale laser beam and material to implement surface treatment, which can be adapted to macro and micro surface treatment of metal components. Process parameters controlling and a reasonable path planning are beneficial to generate useful residual stress distribution and regular geometric morphology, which can significantly change the material wear resistance and improve the anti-fatigue property as well as corrosion resistance. Based on the introduction of principles and characteristics of μLSP technology, the key scientific problems in μLSP process are analyzed, the research progress of shock wave pressure model, related experiments, numerical simulation and surface modification are described, the current existed problems are discussed, and applicative prospect as well as technology development of μLSP is also looked forward.

Laser fusion welding-brazing processes are methods to metallurgically join dissimilar alloys with different melting points by laser heating to melt materials (substrate and filler material) with lower melting point, and by the interaction between the weld pool and the solid substrate with higher melt point at the joint interface. Laser fusion welding-brazing processes of dissimilar alloys are classified according to the laser energy absorption mechanisms. The development and state of the art of laser fusion welding-brazing processes are reviewed.

Laser-arc hybrid welding has absorbed wide interesting in the past years due to its potential industrial applications, in which shielding gas plays an important role to achieve the effective laser-arc synergy effect and stable process. The effects of the shielding gas on the bead quality for laser-arc hybrid welding are reviewed. The mechanisms about the parameters of the shielding gas on process characteristics, bead shape and joint mechanical properties are discussed.

Several special laser processing methods for regulating the mechanical properties of materials are introduced. The so-called laser texturing is to engrave the specify morphology and roughness on the surface of rolls using high-power-density laser. This method can not only improve the performance and function of the rolls, but also improve the performance of the rolled metal sheet by the cold rolling process. Using the laser strengthening method of coating interface, the coating and its interface structure between the coating and the substrate can be optimized through influencing the atomic deposition process while plating. The laser-assisted forming method is using the laser thermal effect to induce the elastic internal stress to do plastic work for forming the parts or improving accuracy of their shape.

With the development of rapid prototyping (RP) technology, the research interests change to direct manufacturing of metal parts with functions. The application fields of RP are expanded to the areas of aerospace, medical, motor vehicle, mould, etc. According to the characteristics of selective laser melting (SLM) applicable for rapid manufacturing of fine-structured and small-lot metal parts, powder materials, process, control, applications and affect factors are studied and discussed by combining the research work of the author′s group. The status-in-art, problems and developing prospect of SLM technology are also discussed.

Machine vision plays an important role in measuring and controlling for laser robot processing. Based on CCD/CMOS, three kinds of machine vision systems for laser remanufacturing robot are developed to reconstruct of 3D-CAD part, temperature field and powder stream field. Their parameters are as follows: scanning width is 200 mm, scanning speed is 10~50 mm/s, deviation is less than 1 mm in 3D-CAD part; measuring temperature regions are 700 ℃~2400 ℃, deviation is less than 50 ℃; measuring powder stream rate regions are 1~100 g/min. They all can realize a real time and online testing and are available in laser remanufacturing robot processing.

The requirement of laser peening of aeronautical turbine blades is introduced, and the relevant research results are described. The surface profile of laser peening with square spots is measured and compared with the case of common circle spots. TC17 titanium blades are treated by laser peening with overlapped square spots, and then the improvement of bend vibration fatigue properties is tested. The key problems of laser peening turbine engine integrally blade rotor (IBR) are researched. The application of laser peening IBR in China is introduced and prospected.

For the hole type changing with laser process parameters, a two-dimensional transient finite model with characteristics of transmission and distribution of beam intensity for laser drilling is established. Numerical simulation research on the hole development is done. The model accounts for the spatial distribution of laser beam and the latent heat of materials phase transformation . The transient thermal field and interface evolution of the hole are showed in the computational analyses. The results show that the depth of the hole increases with the time of laser-material interaction, with the drilling velocity about 1 m/s magnitude, while the hole diameter changes little after the initial increase. The experimental results of various cross-section of the hole type in different parameters are compared with the simulation ones, and they are in good agreement. The hole types include cylindrical type, positive cone type, and inverted cone type. The numerical simulation method calculates the penetration holes and helps to choose appropriate laser parameters.

Achievement of laser close-piercing lapping processing technique for damage-free cutting in arbitrary path (line, curve and angle) of dense Al2O3 ceramics with the thickness of 10～12 mm by CO2 laser is proposed. By the combination analysis of scan electron microscope (SEM) and laser scanning confocal microscope on the cut surface, the good cut quality is concluded. Based on the CCD analysis of the novel cutting processing, the optimal process parameters for damage-free cutting of 10 mm thick Al2O3 ceramics including peak power of 2.7～3.5 kW, pulse frequency of about 50 Hz, cycle duty of 30%～50% and piercing time of 0.1～0.5 s, are obtained. The optimal line cutting speed can be 15～20 mm/min.

Laser cutting of liquid crystal display (LCD) glass substrate is a complex light-induced heat process, in which the temperature plays a vital role. In fracture controlled laser cutting technology, thermal stress is used to induce fissure and break the LCD glass substrate. In order to guide the actual thermal stress laser cutting, as well as reduce the blindness and improve the quality in the cutting process, a numerical simulation is proposed for laser cutting LCD glass substrate. The distribution of temperature is obtained by using finite element analysis software ANSYS. A temperature field numerical simulation is established as laser cutting LCD glass substrate. The effects of laser power and spot diameter on the temperature field are studied and the relationship is obtained. A good cutting profile is obtained in experiment with the help of the numerical simulation results.

The fluidity of molten pool is analyzed with CO2 laser welding on Al-ZL101/TiB2-Al triple plates. Scan electron microscope (SEM) and hardness tester are used to observe the TiB2 distribution and measure the hardness. The fluidity of molten pool is inferred according to the TiB2 distribution and hardness values of weld seam. In the incomplete penetration, a convection loop is presented and the strongest convection locates at the neck of keyhole where the highest hardness and TiB2 volume fraction are presented. In the full penetration, two convection loops are presented on the top and bottom surfaces of molten pool, respectively. The convection is stronger at the bottom than that on the top so that it has higher TiB2 volume fraction and hardness. The slightest convection occurs in the link of two loops, i.e. the center of weld seam where the highest hardness and TiB2 volume fraction are presented because of the smallest reduction of TiB2 flowing away with the convection.

The rapid cooling during laser welding can prompt the occurrence of solidification cracking, however, few study is found on systematic research of solidification cracking during laser welding. It is the key to accurately measure the critical strain and temperature of the crack in order to know solidification cracking susceptibility. By using U-type hot cracking test with in-situ observation method, the occurrence of solidification cracking is captured clearly by high-speed-high-magnification camera. With the in-situ observation method, the local critical strain of crack is measured by tracking the displacement of two reference points near the crack; the local temperature of crack is measured by inserting the thermocouple to the trailing edge of the weld pool. Local critical strains at different temperatures are obtained under different tensile loads in U-type hot cracking test. The high temperature ductility curve is achieved accurately.

Welding pore is the main problem during laser welding of die-cast magnesium alloys. The influences of laser power density and heat input on pore formation regularity during laser welding of die-cast magnesium alloys are studied. The formation regularities of pore are different under low and high laser power densities. Under low laser power densities (less than 1.6×106 W/cm2), porosity increases with the increase of weld heat input; under high power densities(more than 3.2×106 W/cm2), the minimum value of porosity can be obtained at certain weld heat input, and changing weld heat input a bit higher or lower than this certain value both increase porosity, but when the weld heat input is low enough, low porosity can be obtained. The different regularities can be attributed to the influences of laser power density and weld heat input on welding thermal process and the behaviors of gas sources in weld pool. It is found that suppressing the atomic hydrogen precipitation is the key of obtaining low porosity welds.

Welding characteristics of laser-arc double-sided welding (LADSW) for aluminum alloy are studied. Arc physical characteristics are investigated by spectroscopic diagnosis, arc voltage measurement and estimation of electron density by Stark broadening method. With the preheating of tungsten inert gas (TIG) arc, the results show that the weld appearance of laser welding in LADSW is improved, and porosity in weld can be drastically reduced and even eliminated. The shape of weld cross-section can be controlled. Due to the symmetrical weld cross-section and less weld defect inside, the joint of the symmetrical "X" cross-section has the best mechanical properties. The tensile strength is more than 90% of the base metal. Compared with conventional TIG arc, the typical arc shape of LADSW is compressed. There are more metal atoms and less Ar atoms in LADSW arc than those of conventional TIG arc, and the arc voltage is decreased and more stable. The electron density of LADSW is higher than that of conventional TIG arc. The plasma area of laser welding is increased in LADSW compared with conventional laser welding under the same condition.

The laser welding experiments on weld 0.2 mm thickness of the superalloys GH4169 with micro-laser pulse is carried out, the impact of welding process parameters on joints forming is analyzed, and the microstructure and properties of joints are studied by making use of optical microscopy, electronic precision stretching machine, and other analysis and detection methods. The results show that using argon as a shielding gas, 0.2 mm thick GH4169 to the laser as heat source can be successful butt welding with process parameters of the power of 12.8 W, pulse width of 2.7 ms, pulse frequency of 5.0 Hz, and a good welded appearance is formed, and the joint tensile strength is higher than the base metal. The microstructure composed of welded joints is small equiaxed grains in the weld center and columnar grains near the fusion line, and in the heat-affected zone of the joints, there is a black line formation which is similar to the crack after corrosion because of the existence of grain boundary precipitates. Microhardness of welded joints is higher than that of the base metal.

1060 aluminum alloy and T2 copper with the thickness of 3 mm are joined by means of laser penetration-brazing (LPB) with a Yb:YAG disc laser. The mechanical properties of the joint are measured by microhardness and tensile tests. The microhardness of the weld is higher than that of aluminum and copper base metals, respectively, due to the formation of fine grains and hard Al2Cu and Al2Cu3 intermetallic compounds. The results of the tensile tests for welded samples are variational under the same parameters. The maximum failure strength for tensile test is 100.6 MPa. The failure occurres at aluminum side. The minimum failure strength is 94.5 MPa. The failure happens close to the interface due to the hardness gradient and brittle intermetallic compounds.

Experimental investigation of fiber laser welding of automotive aluminum 6016 to galvanized steel DC56D in an overlap configuration is carried out. The effect of the welding speed on penetration depth and tensile shear strength of the joints are studied experimentally. On the other hand, the comparison of the joint strength of the single-weld and that of double-weld assemblies is investigated. The microstructure of the joint and the chemical composition of the intermetallic compounds and the fracture of the tensile specimen are investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) separately. The results indicate that the joint tensile shear strength is great with limiting the penetration depth under appropriate welding speed. The kinds of the intermetallic layer are Fe2Al5, FeAl2 and FeAl3. The double-weld assembly is contributed to improve the joint strength, and the maximum tensile shear strength is 155 N/mm, about 84% of that of the aluminum substrate, which is 26% higher than that of single-weld assembly. In tensile test, the specimen fracture is in heat-affected zone or substrate of aluminum, and the fracture form of the joint is ductile fracture.

The deep penetration laser welding of 20Cr2Ni4A-20 g dissimilar steel is studied to increase the welding efficiency. The effects of laser welding parameters on the morphology of welding seam are investigated using 5 kW Slab CO2 laser. The tensile strength is tested by material testing machine, and the fracture morphologies are observed by scanning electron microscopy. The results show that the welding joint can be optimized by adjusting the defocusing distance, coaxial shielding gas flow rate, laser power and welding speed. The optimum process parameters of 8 mm thickness of 20 g and 20Cr2Ni4A dissimilar steel are: a laser power of 5 kW, a welding speed of 2.5 m/min, a shielding gas of 5 L/min He and 20 L/min Ar and a focusing distance of +2 mm. Under the optimum process parameters, the tensile strength of the welded joint is better than 20 g matrix, which is ductile fracture and the fracture presents dimple.

Galvanized steel and AISI 304 stainless steel are lap-welded by a pulsed-NdYAG laser. The weld joint is of good surface quality based on the shear strength which reaches its work requirement. The effects of the laser welding process parameters such as laser current, welding speed and defocused distance on the shape of the weld seam are investigated. The optimum welding parameters are I=350 A, V=100 mm/min, ΔF=-1 mm,f=4 Hz, W=10 ms, and there is no weld trace on the back of AISI 304 stainless steel at the same time. The microstructure of the welded seam is martensite and residual austenite, and close to the side of galvanized sheet, there is a small amount of pearlite. Because of the existence of martensitic hardened layer, the microhardenss in the weld seam and heat affected zone is higher than that of the base metal.

Laser butt welding of 1.6-mm thick dual-phase high-strength steel B340/590DP is performed by using a 4-kW fiber laser. Weld topography and cross secsion of different butt joint gaps are analyzed. And mechanical properties, microstructure and microhardness of weld are tested. Laser butt joint welding of a three-dimensional body part under optimized process is carried out. Crash tests are performed after welding experiments. The results of laser welding experiments prove that weld with good appearance and narrow heat affected zone (HAZ) can be obtained when butt joint gap is narrower than 18% (about 57.6% of focused spot diameter) of sheet thickness under the proper welding condition. When butt joint gap is narrower than 16% (about 51.2% of focused spot diameter) of sheet thickness, the tensile strength of weld is better than the base metal. Different butt joint gaps have no significant effect on the micro-hardness and microstructure of the weld. The crash tests prove that crash strength of laser welds is in accordance with the design standards. Fiber laser butt welding is better than arc butt welding for a three-dimensional body part.

The pulsed laser welding experiment of Hastelloy C-276 of 0.5 mm thickness is conducted. According to buoyancy force and Marangoni convection, the influences of pulse duration, pulse energy, pulse repetition rate and welding velocity on weld joint are investigated. It is indicated that the pulse energy and welding velocity present the same impact on the forming of weld joint, and suitable parameters can affect the interaction between buoyancy effect and Marangoni convection. The pulse duration can decide the pool liquid flow, and further significantly impact the forming of weld joint. In addition, the variation of repetition rate determines the relative thermal action and impacts the pool flow, and finally varies the weld joint.

The study on bead on plate (BOP) and butt laser welding characteristics of AZ31B-H24 magnesium alloys are carried out by using two lasers, fiber laser and CO2 laser. The effect of different lasers on characteristics is analyzed, from the point of the weld appearances, microstructures and mechanical properties. The results show that fiber laser welded joint has good weld appearance and better suitability. Tensile strength of it can reach 95% of that of base metal, fracture is typically ductile feature, in which dimple is big and deep, while CO2 laser welded joint tends to arise porosity, which sharply decreases its tensile strength, only 47.6% of that of base metal. Fracture mode is mixed mode including ductile and cleavage mode.

Textured poly-crystalline barium dititanate (BaTi2O5, denote as BT2) ferroelectric ceramics with a preferred b-axis orientation are synthesized by a novelty method named laser rapid solidification. So-synthesized BT2 is with a higher density (relative density is larger than 95.1%). The analysis of X-Ray diffraction (XRD) reveals that the samples are of high pure monoclinic phase and the grains grow along the b-axis direction with a reliability high Lotgering factor (0.34～0.48). The observation of scanning electron microscopy (SEM) shows that the so-synthesized ceramics are composed of plate-like microstructure parallel to the laser incident direction. The Curie temperature (Tc) is about 443 ℃. The maximum dielectric constant (εmax, at Tc) is about 6000 at the frequency of 100 kHz. The Curie-Weiss temperature T0 and Curie-Weiss constant are 410 ℃ and 2.08×105 K, respectively.

The Fe75.5C7.0Si3.3B5.5P8.7 amorphous alloy powder is cladded on 304 L stainless substrate by a 5-kW cross flow CO2 laser. The phase, microstructure, thermal stability and microhardness of the coatings are systematically analyzed by optical microscope, X-ray diffractometer (XRD), integrated thermal analyzer and microhardness meter. No crack or void is observed within the coating. The coating has a good metallurgical bond with substrate. The coating mainly consists of amorphous, Fe3P and Fe2Si phases. The microstructure in the near interface region exhibits obvious extensive growth characteristics. A large area of amorphous region is observed in the middle of the coating. The crystallization temperature of the coating begins at 793 K and ends at 835 K. The coating microhardness shows a graded distribution, and the hardest zone is in the middle of the coatings. The highest hardness of the coating is 441.3 HV, which is about 3 times of that of 304 L stainless substrate.

Failure of gear parts can be remanufactured by laser cladding technique, but with the performance of mechanical powder device greatly improved, higher performance of laser remanufacturing gear parts are required. To further improve the performance of laser remanufacturing parts, Fe314 laser cladding coating is duplex treated by the active screen plasma nitriding technique. We focus on the influence of active screen plasma nitriding technique on the laser cladding coating hardness and contact fatigue performance. The results show that Fe314 laser cladding hardness increases from 540 HV to 927 HV and the contact fatigue life increases from 2.42×105 to 4.94×105 after duplex treatment. Obviously, duplex treatment can improve the surface hardness and contact fatigue performance of Fe314 laser cladding coating greatly.

By the same laser cladding process, TiC reinforced H13 matix composite coatings with different contents of TiC particles are fabricated on H13 substrate. The quasi-static tensile properties and stress/strain curves of composite coatings are obtained. The experimental results show that the hardening effect is obvious after stress reaches the yield stress. With higher particle content, the elastic modulus and yield stress increase significantly, but the tensile strength does not change much. With scanning electronic microscope (SEM) observation after tensile fracture, at low content of TiC particles, the fractography distributes a large number of dimples, showing the ductile fracture, but with the increase of particles, the fracture mode changes from ductile to brittle. Based on the Mori-Tanaka mean-field homogenization scheme, coupling with ABAQUS subroutine UMAT, elasto-plastical properties of composite coatings are studied. Theoretical prediction agrees with the experimental results in a certain range of error.

To improve the wear resistance of AZ31B magnesium alloy, laser surface cladding with Al-Si and Al2O3-TiO2 mixture powders (in the mass fraction ratio of 61) is investigated by a CO2 laser. The microstructure, phase analyses and wear behavior of AZ31B modified is studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and wear methods. The XRD pattern shows that the coating is composed of Mg17Al12, Al3Mg2, Mg2Si, Al2O3, TiO2, etc. The average microhardness of the surface layer is significantly improved to 245 HV0.05, as 4 times higher of that of the AZ31B substrate. The coating′s excellent wear resistance is due to the recombination of embedding of ceramic particles and intermetallic compounds. The worn mass of the composite coating decreases by 81.4% compared with that of the substrate.

To obtain more design freedom and realize fast fabrication of mechanisms, a concept of non-assembly mechanism is introduced, which is digitally assembled and later directly fabricated using selective laser melting (SLM) technology. The effect of display on the number of support within the clearance is analyzed when the key points of directly fabrication of metal mechanism are obtained; then the effect of titling display on fabrication quality of clearance is studied. Some specimens with different angles are fabricated under different scanning speeds in order to obtain the critical fabrication angle; for experimental verification, a slider-crank mechanism with a minimum clearance of 0.2 mm is designed and two ones are fabricated by SLM using horizontal display and tilting display respectively under the process parameters of laser power of 150 W, scanning speed of 600 mm/s, powder thickness of 0.035 mm and track space of 0.12mm. Result shows that the slider-crank mechanism can be successfully fabricated by SLM. The methodology of directly fabrication of non-assembly mechanism will allow more design freedom and fast fabrication of mechanisms.

The sample fabricated by laser solid forming (LSF) consists of laser repaired zone (RZ), heat affected zone (HAZ) and forge substrate. The repaired zone consists of coarse columnar β grains which grow epitaxially from the substrate. And β grains are made of extremely fine basket-weave microstructure where a lot of fine acicular α phases precipitate on. Microstructure of heat affected zone transits from duplex microstructure to basket-weave microstructure. After 600 ℃, 1 h furnace cooling annealing continuity of columnar, β grain boundaries have not been affected, and α laths grow slightly and length/width ratio of α laths decreases. Microhardness test shows that hardness value of annealed sample is 5% higher than that of as-deposited sample. The results of high temperature tensile properties and high cycle fatigue property of annealed samples suggest that compared with the forging standard, the tensile strength index is higher while ductility index corresponds to the standard. The fatigue limit is 295 MPa which reaches 70% of the forging standard. At last, failure behavior and fracture mechanism of laser repair samples under different loading modes are analyzed.

"Self-healing effect" is one of the important phenomena in laser metal direct forming (LMDF) process, and plays an important role in improving the forming quality of parts under open-loop control. In order to study the self-healing ability of different materials, reveal main influencing factors, and provide guidance for formulating correct forming process to improve the forming precision, orthogonal experiment is designed to fabricate several thin-walled parts on substrate with "convex" characteristics in LMDF, and the influence of process parameters on sample dimension is analyzed. The experimental results on 316 L stainless steel show that the influence of different process parameters on the self-healing ability varies significantly: the traverse speed is the most important factor, the laser power next, and then the powder mass flow rate. The 316 L stainless steel self-healing ability can be improved remarkably when using optimized laser power, traverse velocity, and powder mass flow rate as 240 W, 6.0 mm/s, and 7.3 g/min, respectively. The maximum self-healing height exceeds 1.54 mm and the self-healing rate is 0.038 mm per layer.

The TiC (mass fraction of 30%) reinforced Ti matrix bulk-form nanocomposites are successfully prepared by selective laser melting (SLM) process. The influence of the applied laser linear energy density η (the ratio of laser power to scan speed) on surface morphology, densification level, microstructure, and mechanical performance of SLM-processed parts is studied. It shows that when η is 400 J/m, the SLM-processed part has a relatively smooth surface. A high relative density of 95.5% and an average microhardness of 750 HV are obtained. The TiC reinforcing phase is dispersed uniformly in the Ti matrix, exhibiting an ultrafine lamellar nanostructure. The dry sliding wear tests reveal that the TiC/Ti nanocomposites possess a considerably low friction coefficient of 0.2, which is much lower than SLM-processed pure titanium parts of 1.2. The densification rate, microhardness, and wear performance decrease at a higher laser energy density of 800 J/m due to the formation of thermal cracks and the coarsening of TiC dendritic reinforcing phase.

Water toughened high manganese steel is treated by laser shocking, and the micro-structure is analyzed by H-800 transmission electron microscope and JSM-5610LV scanning electron microscope. The results show that the hardness of high manganese steel will increase significantly after laser shock processing (LSP) and hardening will occur. The hardness of the impacted center increases from 219 HV to 486 HV, which rises about 122%. In the LSP, a more severe plastic deformation is undergone on the materials, a large number of dislocations are generated, and thus the dislocation block and the cellular structure of dislocations form. With the deformation increasing, a large number of twins are generated in the structure. So the grain boundaries, phase boundaries and other interfaces are destroyed by twinning and dislocation interaction, and grain refinement forms. Dislocations and twins share the role with the fine grain strengthening, so a substantial increase of the performance is emerged in high manganese steel.

Experimental research of nano-hardness and elastic modulus of copper treated by micro laser shock peening (μLSP) is carried out. The results show that nano-hardness and elastic modulus treated by μLSP are higher than those of substrate, with the maxima of 4.21 and 2.39 times, respectively. Change laws of nano-hardness and elastic modulus in shock region are explored, and main factors and strengthening mechanism are discussed. With reasonable characterization of surface mechanical performance by nanoindentation technique, good guidance on parameter optimal selection for further study of surface mechanical performance in μLSP is provided.

Fabrication of nanoporous coatings is investigated by a two-step process involving high power laser cladding of homogeneous Cu40Mn60 alloy coatings followed by selective electrochemical de-alloying. Cu-Mn alloy coatings with fine shape, low dilute ratio and refined microstructure are fabricated on mild steel by means of laser processing. The second dendrite arm spacing (SDAS) decreases with the increase of laser remelting speed. Auger mapping results indicate that nanoporous manganese is obtained by selective electrochemical etching of the less active Cu component owing to the passivation of the more active manganese in potassium nitrate solution. The microstructure and homogeneity of the precursor Cu40Mn60 alloys have a significant influence on the evolution of nanopores during selective electrochemical de-alloying. The surface morphology of the porous Mn is a ribbon-like structure with thickness up to 2 μm.

The stainless steel sheet of AISI-201 is shocked by means of Q-switched Ndglass laser setup with the 1064 nm output wavelength, 20 ns short pulse and 5 mm beam spot in diameter. The microstructure evolution of the shocked layer is analyzed by using the thermo-field emission scanning electron microscope (TESEM) and transmission electron microscope (TEM). The nano-crystallization behavior induced by laser shock and the mechanism are analyzed, as well as the effect on surface hardness. The experimental results demonstrate that the nano-crystalline grains with 20~50 nm in diameter are obtained on the surface layer up to the depth of 300 μm of the shocked stainless steel AISI-201, and the amorphous phase is also observed around some nano-crystalline grains. The hardness of the nano-crystallized surface is increased by 36% in comparison with the matrix of the stainless steel. It is considered that nano-crystallization process results from the co-action of grain′s smashing up and crystal′s defects of original austenite grains under the combination effect of the super strain rate and super-high power of laser shocking.

In order to study the special optical absorption efficiency of “black silicon” materials, “black silicon” material with different heights of micro-cones is successfully fabricated, and the geometric parameters of the micro-cones are measured by scanning electron microscope (SEM). Then a model is built to calculate the surface effective absorption area of “black silicon” material based on the measured structure of “black silicon” material, and the surface area of “black silicon” is more than 20 times than that of normal silicon. Meantime, according to the geometrical optics method, the reflectivity is simulated during the wavelength from 200 nm to 2000 nm. The simulation results are relatively close to the experimental results. It is theoretically verified that the strong optical absorption ability of the silicon with micro-nano structure is due to special structure for light trapping effect and the increase of surface effective absorption area.

CO2 laser direct-writing ablation micromachining technique is used to fabricate the microchannel on the polymethyl methacrylate (PMMA) substrate. The correlation between the process parameters (the beam translational velocity and the processing number of times) and the micromachining quality (the width and the depth of the microchannel) is investigated. For a given processing times, the depth and width of microchannel both decrease along with the enhancement of beam translational velocity. At fixed beam translational velocity, the depth and width are direct proportion to the processing times, respectively. The microchannel is fabricated on different PMMA substrates with smooth surface, rough surface and surface adhering water. The micromachining quality and the surface roughness of the microchannel are compared. The microchannel with a hydraulic diameter of 80 μm is fabricated under two experimental conditions, and the comparative experiment has been performed on the microchannel with the relative roughness. It is found that the relative roughness is minished effectively when a laser is used to make ablation of the microchannel on the PMMA substrate with surface adhering water. The improved fabrication procedure will be used to increase the availability of CO2 laser direct-writing ablation technique on the micromachining of the PMMA microfluidic chip.

The processings of laser energy absorption and thermal conduct are analyzed, and a mechanism of metallic film/composite substrate interface separation while metallic film in solid state due to the composite material thermal decomposition is also proposed subsequently. A new method of improving laser ablation accuracy using this mechanism and laser power distribution transform technology is proposed. Laser wavefront diffraction transform technology is employed to convert the ablation laser power density and its distribution, and the confirmed experiment is carried out.

In order to reduce the recast layer of the laser etching crater and to increase the etching depth the effect of laser pulse width and waveform on laser etching crater morphology is studied by using double acousto-optic modulation technique, comparing the pulse widths with 0.25, 7.5 and 200 μs, and comparing different waveforms with single peak, two peaks and three peaks. The results show that when the pulse width is 0.25 μs, the burr is more; when it is 200 μs, significant surface melting phenomenon appears; and when it is 7.5 μs the phenomenon of surface melting and the burr are significantly reduced. The surface of laser wave etching with a single peak has more burr with the depth of 7.5 μm, the one with three peaks appears the surface melting phenomenon with the depth of 10 μm, and when using two peaks waveform etching, the surface of burr and melting are the least, and the depth is 15 μm.