选区熔化Ti-6Al-4V合金热行为及成形质量研究

Research on Thermal Behavior and Forming Quality of Selective Laser Melted Ti-6Al-4V Titanium Alloy

基于有限元分析方法对激光选区熔化Ti-6Al-4V钛合金过程热行为进行数值模拟,研究了扫描间距对成形过程热行为的影响机制。模拟与实验相结合,揭示了扫描间距对热行为及成形质量的影响机制,探讨了热行为与成形质量内在联系。结果表明,随着扫描间距从60μm增加至150μm,熔池温度逐渐降低,熔池尺寸逐渐减小,液相存在时间逐渐缩短,而冷却速率逐渐增大。扫描间距太小,熔池过热,导致"球化";扫描间距过大,扫描道之间搭接率过低,不利于致密化。当扫描间距为60μm时,制件表面"球化"严重,内部针状马氏体相对粗大;当扫描间距为150μm时,制件表面呈明显"沟壑"状,内部针状马氏体相对细小。

The finite element numerical simulation of thermal behavior during selective laser melting(SLM) of Ti-6Al-4V titanium ally was investigated, and the influence of hatch distance on the thermal behavior was mainly studied.Based on the combination of simulation and experimental results, the influence mechanisms of hatch distance on the thermal behavior and forming quality were revealed, and the relation of thermal behavior and forming quality was discussed. The results show that as the hatch distance increases from 60 μm to 150 μm, the temperature and the size of the molten pool decrease gradually. Furthermore, with the increase of hatch distance, the cooling rate increases and the liquid life time decreasee inversely. The too small hatch distance leads to the overheating molten pool, which result in the balling phenomenon. In comparison, the too large hatch distance leads to the insufficient overlap, which result in the lower relative density. When the hatch distance is 60 μm, the spheroidization on the surface of the parts is serious, and the acicular martensite inside is relatively large. When the hatch distance is 150 μm, the surface morphology of the part is in gully type and the inner needle type martensite is relatively fine.