Er元素添加对SLM成型高强铝合金组织和性能的影响

Impact of Erbium on Microstructure and Properties of High-Strength Aluminum Alloys Fabricated by SLM

为解决高强铝合金增材制造技术中遇到的高热裂倾向性问题,提出一种新的合金成分设计,即在传统的高性能Al-Zn-Mg-Cu铝合金中添加1.41 at.%Er(超过共晶成分点),并研究添加Er后对成型缺陷(裂纹、孔隙、变形等)、晶粒微观结构及力学性能的影响。结果表明,在适当的工艺参数下,选择性激光熔化(SLM)可以制备出无明显裂纹的、致密、高强度的Al-Zn-Mg-Cu-Er合金样品。X射线衍射仪(XRD)还发现,Al3Er相存在于Al-Zn-Mg-Cu-Er合金样品之中。结合Thermo-Calc软件的模拟结果及电子背散射衍射(EBSD)分析,认为超过共晶成分点的Er造成了Al3Er初生相的形成,后者可以作为α-Al理想的异质形核位点,并促使α-Al晶粒大量形核,引起平均晶粒尺寸的骤降、晶型由柱状晶向等轴晶转变、晶粒取向分布更随机,最终改善热裂倾向性、提升合金的强塑性。

In order to address the high hot-cracking propensity encountered in the additive manufacturing of high-performance Al alloys,a novel alloy composition design was proposed,that is,1.41 at.%Er(exceeding the eutectic composition point)was added to a conventional high-performance Al-Zn-Mg-Cu alloy,and the effects of Er addition on processing-related defects(cracks,porosity,distortion,etc.),grain microstructure,and mechanical properties were studied.The results show that using appropriate processing parameters,selective laser melting(SLM)can produce free-of-cracks,dense,and high-strength Al-Zn-Mg-Cu-Er alloy samples.Through X-ray diffraction analysis,it is also found the existence of Al3Er phase in the samples.Combined with the simulation results of Thermo-Calc software and electron backscatter diffraction(EBSD)analysis,it is concluded that the hyper-eutectic amount of Er enables the formation of Al3Er primary phase.The latter acts as ideal heterogenous nucleation sites forα-Al,and thus promotes high-density nucleation ofα-Al grains,which causes the significant reduction of average grain size,columnar-to-equiaxed grain structural transition,and a more random distribution of grain orientation,therefore improving hot-cracking propensity,strength,and ductility.