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Preparation, microstructure, and microhardness of selective laser-melted Wa??3Ta sample
摘要： Tungsten (W) alloy is of difficulty in processing for conventional way because of its high melting point. Here, W alloy sample with the addition of 3 wt% Ta was prepared by selective laser melting. The influence of volumetric energy density (VED) on the surface morphology and the relative density was discussed, and microstructure, phase composition, and microhardness were investigated. The results show that a smooth surface and high relative density (95.79%) can be obtained under optimal VED. The W–Ta substitutional solid solution formed because of the replacement of Ta atom. There are strip and block fine grains in the W–3Ta sample with no significant texture. In addition, subgrain structure with a size of around 1 lm formed inside the strip grain, owing to the large thermal gradient and extremely fast cooling rate. Finally, the W–3Ta alloy shows higher microhardness than that obtained by traditional methods.
关键词： tungsten alloy,volumetric energy density,microstructure,microhardness,selective laser melting
更新于2025-09-23 15:19:57
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Mesoscopic-scale simulation of pore evolution during laser powder bed fusion process
摘要： Laser powder bed fusion (LPBF) is an advanced manufacturing technology that uses data-driven, layer-by-layer accumulation of materials to form metal components and has been widely applied in aerospace and other fields. Effectively controlling pore defects is a key scientific problem and technical difficulty in LPBF industrial production. Based on the open-source discrete element method code Yade, the particle distribution of the powder bed was obtained. Based on the open-source computational fluid dynamics code OpenFOAM, the pore evolution during the LPBF formation process at the mesoscopic scale was predicted. The thermal–force factors affecting the molten pool included the surface tension, Marangoni effect, gasification recoil force, and mushy drag force. The laser energy model used a body heat source based on interface tracking. First, dimensionless analysis of the molten pool evolution in the case of LPBF single-track formation was carried out. The molten pool evolution was mainly influenced by the gasification recoil force, Marangoni effect and surface tension, and the main influencing factors on different zones of the molten pool were different. To examine the influences of the laser power, scanning speed, powder bed thickness, and hatch space on the pore defect in the LPBF formation process, simulations were carried out and compared with experimental results. When the volumetric energy density was too small, pore defects occurred due to insufficient fusion of metal particles, and when the volumetric energy density was too large to cause the “keyhole” effect, pore defects occurred because the entrained gas could not escape in time. This paper is expected to provide theoretical guidance for the scientific regulation of pore defects in LPBF production.
关键词： OpenFOAM,Volumetric energy density,Dimensionless analysis,Pore defect,Laser powder bed fusion,Numerical simulation
更新于2025-09-19 17:13:59