不同成形方式对WE43镁合金组织和力学性能的影响

Influence of Different Forming Methods on Microstructure and Mechanical Properties of WE43 Magnesium Alloy

采用激光选区熔化成形(SLM)、铸造及挤压方式制备了WE43镁合金试样,通过维氏硬度计、密度测试计、光学显微镜、扫描电镜以及拉伸试验机等设备分析了不同制备方式下WE43镁合金的宏微观组织和力学性能变化规律;设计了基于指数函数的模型对不同成形方式的WE43应力–应变曲线进行统一拟合,为WE43材料未来增材、减材以及等材工艺复合制造复杂零件打下基础。结果表明,SLM成形WE43有明显的各向异性,铸态和挤压态不明显。SLM成形WE43镁合金的强度最高,抗拉强度达到313 MPa,是铸态的183%;挤压态WE43镁合金塑性最好,伸长率达到10.2%,是铸态的232%;此外,SLM态镁合金密度只有1.731 g/cm^(3),仅为挤压态的85.7%和铸态的95.2%。在断裂特性上,SLM态和挤压态为韧性断裂,而铸造态为脆性断裂。在内部存在20μm左右孔洞形缺陷的情况下,SLM成形镁合金依然具有最高的强度,主要原因是SLM成形WE43镁合金平均晶粒尺寸仅为2.6μm,基体内存在大量的稀土相沉淀以及纳米级亚稳相。由此可知,通过进一步的后处理方法焊合SLM态镁合金内部孔洞形缺陷后,材料力学性能可以大幅提高。

Using laser selective melting forming(SLM),casting,extrusion way prepared WE43 magnesium alloy specimens,through the Vickers hardness tester,density tester,optical microscope,scanning electron microscope,as well as tensile tester and other equipment to analyze the macro and microstructure and mechanical properties of the different preparation way forming WE43 magnesium alloy change rule.The models based on exponential function were designed to uniformly fit the stress–strain curves of WE43 with different forming methods,which laid a foundation for the future composite manufacturing of complex parts by additive,subtractive and equal material processes of WE43.The results show that SLM forming WE43 magnesium alloy has the highest strength,the tensile strength reaches 313 MPa,which is 183% of the casting state;extruded state of WE43 magnesium alloy has the best plasticity,the elongation rate reaches 10.2%,which is 232% of the casting state;the density of magnesium alloy of the SLM state is only 1.731 g/cm^(3),which is only 85.7% of the extruded state,and 95.2% of the casting state.The SLM state and the extruded state are ductile fracture,while the casting state is brittle fracture.SLM-formed WE43 has obvious anisotropy,the casting state and extruded state is not obvious.In the presence of a large number of hole-shaped defects around 20μm,SLM-formed magnesium alloys still have the highest strength,mainly due to the average grain size of SLM-formed WE43 magnesium alloys of only 2.6μm,the large amount of rare-earth phase precipitation present in the matrix,and the nanoscale sub-stable phases.It can be seen that the mechanical properties of the material can be significantly improved after welding and closing the internal hole-shaped defects in the SLM state magnesium alloy by further post-treatment methods.