选择性激光熔化技术(Selective laser melting, SLM)是近十几年发展的一种利用高能激光束熔化金属粉末, 堆叠成型的先进快速成形技术。目前, 国内外对铝合金SLM成形的研究主要集中在Al-Si系粉末, 对于7系超高强度铝合金粉末SLM成形的研究还处于起步阶段。研究使用7075铝合金粉末对SLM成形工艺做了一系列试验, 利用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)等仪器分析了7075铝合金选择性激光熔化成形试样的组织性能和裂纹。结果表明, 试样中的裂纹是由成分偏析所造成的, 偏析导致非平衡第二相T相和η′(MgZn2)相析出; 并且随着激光能量密度的增加, 试样中的柱状晶长度、熔池深度、裂纹平均长度、试样抗拉强度都随之增大, 而裂纹数量随之减少。

The selective laser melting (SLM) is an advanced rapid prototyping technology developed in recent decades by using high energy laser beam to melt metal powder layer by layer. At present, the research on aluminum alloy by SLM at home is mainly concentrated on the Al-Si powder, and the research on the 7 series ultra-high strength aluminum alloy by SLM is still in the initial stage. A series of experiments were carried out on 7075 aluminum alloy powder for the SLM forming process. The microstructure properties and cracks of the 7075 aluminum alloy by SLM samples were analyzed by means of metallographic microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and other instruments. The results show that the crack in the sample is caused by component segregation, second T phase and η′(MgZn2) phase non-equilibrium phase precipitate because of component segregation. And with the increase of the laser energy density, the columnar crystal length, the depth of the molten pool, the mean length of the crack and the tensile strength of the sample increase, the number of cracks decreases.