激光选区熔化AZ91D镁合金的微观组织与力学性能

Microstructure and mechanical properties of AZ91D fabricated by selective laser melting

采用激光选区熔化技术(Selective laser melting,SLM)制备了AZ91D镁合金试样,研究了成形过程中体能量密度对AZ91D试样的影响,采用光学显微镜(OM)、主要扫描电子显微镜(SEM)、透射电子显微镜(TEM)和力学性能测试等方法,对SLM AZ91D合金的微观组织、物相和力学性能进行分析。结果表明,在功率为130 W、扫描速度为300 mm/s、体能量密度为144.44 J/mm^(3)时,所得试样的致密度最佳。SLM AZ91D试样中存在α-Mg、β-Mg_(17)Al_(12)两相,并且熔池边缘由蜂窝状的等轴晶和柱状晶共同组成,与铸态AZ91D试样的微观组织和力学性能进行对比,SLM AZ91D试样的晶粒更细小(平均晶粒尺寸约为1.013μm),且显微硬度(97.10HV_(0.1))及抗拉强度(316 MPa)均高于铸造态AZ91D试样(76.61HV_(0.1);208 MPa)。

A series of AZ91D magnesium alloy specimens were fabricated using selective laser melting(SLM)technology to investigate the effect of volumetric energy density on the micro-defects distribution of the AZ91D specimens.The microstructural evolution,main phases and mechanical properties of the SLM AZ91D samples were characterized by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and mechanical properties tests.The results show that the densities of the specimens were the highest with the power of 130 W,scanning speed of 30 mm/s,and volumetric energy density of 144.44 J/mm^(3).The phase composition of SLM AZ91D alloy is confirmed asα-Mg andβ-Mg_(17)Al_(12),phases.The melt pool edge is composed of the honeycomb-like structure of equiaxed grains and columnar grains.Comparing with the as-cast AZ91D specimen,the grain size of the SLM AZ91D specimen is finer than that of the as-cast AZ91D specimen(average grain size of 1.013μm),and its microhardness(97.10HV_(0.1))and tensile strength(316 MPa)are higher than those of the as-cast AZ91D specimens(76.61HV_(0.1);208 MPa).