SignificanceLarge-area multi-laser powder bed fusion (LAM-PBF) has emerged as a transformative technology within the domain of metal additive manufacturing. It effectively overcomes the inefficiencies and size limitations inherent in the traditional selective laser melting (SLM) process. Although SLM is renowned for its precision and exceptional quality of the components it produces, its relatively slow processing speed and limited build volume are considered significant impediments, particularly in the aerospace and energy industries. These fields often require the manufacture of large and complex parts, which SLM is unable to produce efficiently. LAM-PBF addresses these challenges by employing multiple synchronized lasers to expand the scanning area, thereby significantly enhancing the forming efficiency. This innovation facilitates the production of components on a meter scale and signifies a tremendous advancement in manufacturing capabilities. In addition to mere efficiency gains, LAM-PBF has catalyzed advances across various domains, including materials science, process optimization, and intelligent manufacturing.ProgressThe development of novel LAM-PBF equipment has played a pivotal role in enhancing efficiency. The EP-M2050 system exemplifies these advances by offering an impressive build volume of 2058 mm×2058 mm×1100 mm and incorporating 36‒64 lasers to achieve a maximum efficiency of 1080 cm³/h. Similarly, GE’s ATLAS system demonstrates the potential of LAM-PBF technology by producing 150 parts simultaneously, thereby reducing the cycle time by a remarkable 75%. These achievements can be attributed to various innovations, such as the adoption of long-focus f‒θ lenses, the coordination between multiple lasers, and modular designs that enhance flexibility and scalability. Another crucial strategy that boosts efficiency is the optimization of the layer thickness. Increasing layer thickness, typically within the range of 120‒150 μm, facilitates higher deposition rates. However, this approach may result in problems such as grain coarsening and porosity. Research has shown that upon the optimization of parameters, 316L stainless steel can achieve a relative density of 99.99% and a deposition rate of 8.1 mm³/s, thereby effectively doubling the traditional efficiency. Nevertheless, a balance must be ensured between the thickness of layers and the microstructure uniformity of the steel to ensure that the mechanical properties of a final product satisfy the required standards. SmartScan algorithms have emerged as a valuable tool in this context by optimizing scan sequences to stabilize thermal fields, thereby reducing the residual stress by more than 50%. These algorithms greatly contribute to enhancing the overall quality and performance of manufactured parts. Further, numerical simulation tools like OpenFOAM and ABAQUS have proven to be indispensable. They are used to simulate temperature fields, the dynamics of melt-pools, and stress distributions with remarkable accuracy, thereby guiding process optimization with errors below 6.3%. Such simulations provide critical insight for refining manufacturing parameters, which ultimately yields improved outcomes. For quality control and defect mitigation, wind field design has emerged as a key factor. The optimization of the wind field can minimize spatter-induced defects, which are a frequent concern in additive manufacturing. Innovations such as waveform inlet structures and reverse airflow scanning can reduce spatter by 30%, thereby improving surface quality. Computational models have further supported these efforts by revealing that an energy input greater than 0.78 × 10⁶ W/cm³ increases the spatter height to 8 cm. These findings underscore the need for dynamic airflow-laser coupling studies to better understand and control such phenomena. Hexagonal and sinusoidal scan paths represent additional advancements in this regard, as they reduce porosity to as low as 0.5% while simultaneously lowering the residual stress. These paths are designed to optimize energy distribution and minimize thermal gradients, thereby producing more uniform and defect-free components. Staggered splicing techniques, such as an interlayer rotation of 67°, can effectively mitigate overlap defects caused by oxidation and thermal gradients. These techniques enhance the structural integrity of the final product and render it more suitable for demanding applications. Dual-beam interactions present both opportunities and challenges. Although they enhance the efficiency and quality of processing, they also necessitate real-time monitoring to control splatter and melt-pool instability. This underscores the importance of integrating both advanced monitoring systems and adaptive control mechanisms into the manufacturing process. Thus, LAM-PBF has achieved significant progress in terms of both efficiency and quality through continuous equipment innovations, meticulous process optimization, and comprehensive multi-physics modeling.Conclusions and ProspectsSeveral promising directions of research warrant further exploration. The development of advanced equipment, such as modular and intelligent systems that are automated and equipped with high-precision sensors, holds considerable potential for achieving industrial scalability. Multi-field coupling studies on airflow-laser interactions are needed to establish dynamic energy balance criteria to guide process optimization in real-time. Moreover, artificial intelligence-driven optimization, wherein machine learning algorithms facilitate real-time adaptive scanning and defect prediction, presents an exciting frontier. This integration of artificial intelligence could enhance manufacturing precision and greatly reduce defect rates. Material innovation remains another critical area with the development of high-strength alloys like Al-Sc and Ti6Al4V, which own optimal absorption and flow properties. These materials are expected to expand the scope of application of LAM-PBF, thereby enabling the production of components that exhibit superior mechanical performance. By addressing these challenges and embracing innovative solutions, LAM-PBF is expected to unlock new possibilities in high-performance, large-scale additive manufacturing. This will be beneficial to established industries like the aerospace and energy industries while paving the way for emerging sectors that require efficient and precise manufacturing capability.

ObjectiveThe TA15 titanium alloy is an important aerospace material that is extensively used for the manufacturing of aircraft structural parts. As aircraft missions over the sea have become more frequent in China, airframe components have become prone to electrochemical corrosion owing to factors related to the humid marine atmosphere. Simultaneously, the surfaces of the aircraft components are susceptible to damage from external objects during operation, leading to failure. Therefore, improving the surface properties of materials is crucial for extending the service life of critical parts. Currently, surface modification of materials can be achieved using surface-strengthening technologies. Laser shock peening (LSP) offers advantages such as high efficiency, controllability, and precision. It can introduce a larger compressive residual stress (CRS), has smaller impact on the surface roughness, and does not compromise the surface integrity of a material. Hence, we perform surface strengthening on the TA15 alloy using LSP, and conduct in-depth research and comparative analyses of the microstructural evolution of TA15 titanium alloys with different microstructures after surface modification. This can provide a theoretical basis and technical support for improving the corrosion resistance of TA15 titanium alloys and extending the service life of aircraft structural components.MethodsFirst, TA15 titanium alloy was subjected to heat treatment to obtain equiaxed and basketweave microstructures. Subsequently, the specimens were subjected to LSP. A phase analysis was performed using X-ray diffraction (XRD). The microstructure of the TA15 titanium alloy was observed using optical microscopy (OM) and transmission electron microscopy (TEM). The surface roughness of the specimens was measured using a 3D profilometer. The hardness and residual stress were measured using a microhardness tester and a residual stress analyzer, respectively. Electrochemical performance tests were performed using an electrochemical workstation, and the corrosion rate of the material was determined through static immersion experiments. The corrosion morphology was observed using scanning electron microscopy (SEM) to reveal the corrosion mechanism.Results and DiscussionsAfter LSP, a severe plastic deformation (SPD) layer with a certain thickness is formed on the TA15 titanium alloy specimens (Fig. 3). Numerous crystal defects, such as dislocations, are generated in the microstructure (Fig. 4). The surface grains are refined into nanocrystals via a dislocation segmentation mechanism (Fig. 5). After LSP, the surface microhardness of the specimens with equiaxed and basketweave microstructures increases by 16.7% and 15.7%, respectively (Fig. 7). Along the depth direction, the microhardness and CRS exhibit gradient changes owing to the gradual decrease in the shock wave energy, with the maximum values occurring at the specimen's surface. After LSP, the corrosion current of the TA15 titanium alloy decreases (Table 3), corrosion rate decreases (Fig. 13), and the corrosion resistance improves. Grain refinement leads to a faster rate of formation of the surface passivation film that enhances its ability to resist corrosive media. The high-amplitude CRS on the surface inhibits corrosion.ConclusionsIn this study, LSP was performed on a TA15 titanium alloy with equiaxed and basketweave microstructures. The microstructural changes before and after LSP, as well as the corrosion performance in 3.5% NaCl and 5 mol/L HCl solutions, were comparatively studied. LSP does not change the microstructural composition of the material; however, the material undergoes SPD. As the energy of the laser shock wave energy gradually attenuates with increasing depths from the surface, a gradient microstructure is formed along the depth direction, and the microhardness and residual compressive stress exhibit decreasing gradient characteristics. The corrosion resistance of the TA15 titanium alloy follows the order of equiaxed microstructure > basketweave microstructure. After LSP, the thicknesses of the SPD layer thicknesses of the specimens with equiaxed and basketweave microstructures are 41 and 33 μm, respectively, and the surface grains transform into nanocrystals. Grain refinement and increased grain boundaries provide more nucleation sites for the passive film, accelerating its formation and enhancing the corrosion resistance of the TA15 titanium alloy. The reduction in surface roughness decreases the corrosion rate, whereas the high-amplitude CRS generated on the surface delays the initiation and propagation of corrosion cracks, further improving the corrosion resistance of the alloy.