铜粉激光烧结致密化过程数值模拟

Micro-densification mechanism of copper powder in laser sintering

通过建立金属粉末直接激光烧结过程的微观模型,对铜粉激光烧结行为进行数值模拟和实验研究,探索激光烧结致密化特征及烧结工艺、材料物性等对烧结过程和质量的影响。结果表明:激光烧结过程主要经历2个阶段:第一阶段表现为孔隙在金属熔体中的消除(约10-4s),实现快速致密化;第2阶段为熔膜的铺展或收缩引起形貌变化,但熔体中仍残留微孔,致密度基本不变。熔体表面张力、粘性、润湿性和熔膜厚度等因素对致密化进程有不同程度的影响。

Based on a microcosmic model of direct metal laser sintering（DMLS）, the sintering process of copper powder by simulation and experiment was investigated for exploring some process parameter＇s effect on sintering processes and qualities. It is shown that the process of laser sintering can be divided into two stages： 1） escaping stage of pores： during this process, small pores unite together forming big holes and being escaped, as a result, the density increases quickly; 2） changing stage of the melt： there are still tiny pores stayed in the melt, the densification changes little, and the shape of the melt changes for the spreading and shrinking behavior. Surface tension and viscosity of the melt, wettability, especially the thickness of the melt film have significant influence on the densification process.