激光选区熔化成形制备高强Al-Mg-Sc合金的组织与性能

Microstructure and properties of high-strengthAl-Mg-Sc alloys fabricated by selectivelaser melting

通过综合分析硬度、电导率与拉伸性能等宏观特性及微观形貌特征,探讨激光选区熔化成形(selective laser melting,SLM)工艺参数与后期时效处理对SLM制备Al-3.4Mg-1.08Sc合金的微观组织、过饱和度及第二相析出行为的影响机理。利用致密度与硬度的变化规律,最终优化得到最佳的SLM工艺参数与时效制度。结果表明:实验制备的Al-Mg-Sc合金的微观组织由超细等轴晶及其周围相对较粗的柱状晶组成,合金在金相显微镜下可观察到熔池堆叠的形貌特征;Al-Mg-Sc合金在基板温度35℃下最佳的SLM制备工艺为扫描速率1600 mm/s、激光功率370 W。300℃下最佳时效时长为12 h,经过峰时效处理后实验合金的屈服强度可达479.0 MPa。在SLM快速冷却条件下,Al-Mg-Sc合金内部形成过饱和固溶体,在制备与热处理过程中析出大量的纳米级Al3(Sc,Zr)粒子,使得Al-Mg-Sc合金具备优异的力学性能;细晶强化与第二相强化是SLM制备Al-Mg-Sc合金展现出优异性能的主要原因。

By comprehensive analysis of macroscopic characteristics of hardness,electrical conductivity and tensile properties and features of microcosmic morphology,the influence mechanism of process parameters of laser selective melting and following aging treatment on the microstructure,supersaturated solid solution and second-phase precipitation behavior of Al-3.4Mg-1.08Sc alloy fabricated by SLM was discussed.By utilizing the change rules of density and hardness,finally the optimum SLM process parameters and aging system were obtained.The results show that the microstructure of the Al-Mg-Sc alloy fabricated in this experiment is composed of ultrafine equiaxed grains and relatively coarser columnar grains around.The optimal fabrication parameter of Al-Mg-Sc alloy fabricated at platform temperature of 35℃is conducted with scanning speed of 1600 mm/s,laser power of 370 W.The optimum aging time is 12 h at 300℃,the yield strength of studied alloy can reach 479.0 MPa through peak aging treatment.Under rapid cooling rate of SLM process,supersaturated solid solution is formed in Al-Mg-Sc alloy,and a large number of nanometer Al 3(Sc,Zr)particles are precipitated during the fabrication and heat treatment process,which makes the Al-Mg-Sc alloy present excellent potential of mechanical properties.The fine grain strengthening and the second phase strengthening are the main factors for exhibiting properties of Al-Mg-Sc alloy fabricated by SLM.