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Densification of pure copper by selective laser melting process
摘要： Pure copper is utilized as a material for products with complicated shape and high thermal conductivity such as heat exchangers. However, it is difficult to fabricate pure copper parts with high density by the selective laser melting (SLM) process. One of the reasons is considered to be its high thermal conductivity by which the heat in the melt pool rapidly diffuses away. Additionally, the lower rate of energy absorption of fiber laser power for pure copper makes the size of melt pool smaller. In this research, the optimum fabrication condition of high-purity 99.9% copper fabricated by SLM process was investigated by evaluating the density and microstructure. As a result, it was found that the optimum condition of laser power and scan speed are 800~900W and 300 mm/s, respectively, and the optimum energy density is around 1000 J/mm3, which is much higher than that of other materials due to high reflectivity and high thermal conductivity of pure copper. And also, it was found that the hatch pitch is important factor to achieve the densification of the as-built specimen and the optimum hatch pitch was 0.01 mm. The high density parts were successfully fabricated by the optimum fabrication condition. The maximum density of the as-built specimen was 96.6 % and was much higher than that of the as-built part already reported.
关键词： Microstructure,Copper,Density,Process parameter,Additive manufacturing
更新于2025-09-23 15:19:57
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Effect of Interlayer Cooling Time, Constraint and Tool Path Strategy on Deformation of Large Components Made by Laser Metal Deposition with Wire
摘要： Laser metal deposition with wire (LMD-w) is a developing additive manufacturing (AM) technology that has a high deposition material rate and efficiency and is suitable for fabrication of large aerospace components. However, control of material properties, geometry, and residual stresses is needed before LMD-w technology can be widely adopted for the construction of critical structural components. In this study, we investigated the effect of interlayer cooling time, clamp constraints, and tool path strategy on part distortion and residual stresses in large-scale laser additive manufactured Ti-6Al-4V components using finite element method (FEM). The simulations were validated with the temperature and the distortion measurements obtained from a real LMD-w process. We found that a shorter interlayer cooling time, full clamping constraints on the build plates, and a bidirectional tool path with 180° rotation minimized part distortion and residual stresses and resulted in symmetric stress distribution.
关键词： Ti-6Al-4V,part deformation,process parameter optimization,interlayer cooling time,large-scale additive manufacturing
更新于2025-09-16 10:30:52
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Correlation of Process Parameters and Porosity in Laser Welding of 7A52 Aluminum Alloy using Response Surface Methodology
摘要： The article presents an experimental investigation of the effect of process parameters (i.e. laser power, welding speed and defocus distance) on porosity in laser welding of 7A52 aluminum alloy. A three-factor, three-level factorial Box–Behnken design (BBD) of response surface methodology (RSM) was used to complete the design matrix with the objective of optimizing the process parameters. Multiple regression models were established to predict the correlation between the selected process parameters and porosity, and then were tested for adequacy using analysis of variance (ANOVA). The results showed that macro pores in laser welding seam were mainly keyhole induced, and porosity susceptibility was mostly dominated by welding speed. The optimal combination of process parameters is the laser power of 3.5kW, welding speed of 10.0mm/s, and the defocus distance of +4.0mm. Under the optimal process parameters, superior weld seams without macro pore were produced. The predicted porosity area fraction with RSM models was confirmed to be in good agreement with the measured values of validation experiments.
关键词： process parameter,response surface methodology,porosity,7A52 aluminum alloy,laser welding
更新于2025-09-16 10:30:52
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Investigation on geometric precision and surface quality of microholes machined by ultrafast laser
摘要： The geometric precision and surface quality of film cooling holes has significant influence on the cooling efficiency and fatigue life of turbine blades. In this paper, the investigation about fabrication process of film cooling holes on the single crystal superalloy DD6 plate specimen by ultrafast laser is carried out. By comparing three different processing paths, minimum roughness of hole wall could be obtained by concentric circular scanning, which was used in the followed-up experiment. The influence of process parameters on the geometric precision and surface quality of microholes was analyzed, and the physical mechanism was examined. The results show that among several process parameters, focus position has the most significant influence on the microholes geometric precision and surface quality, and that the divergent beam (where the focal plane is above the machined surface) can lead to smaller taper, roundness, and surface roughness. In addition, besides a layer of solidified debris adheres to the inner wall at the hole entrance, the microholes machined by ultrafast lasers have no other defects such as a recast layer, microcrack or heat affected zone.
关键词： Geometric precision,Surface quality,Process parameter,Ultrafast laser,Microhole drilling
更新于2025-09-12 10:27:22