激光选区熔化与铸造成形TC4钛合金的力学性能分析

Analysis of Mechanical Properties of TC4 Titanium Alloy Formed by Laser Selective Melting and Casting

借助有限元模拟、光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)和维氏硬度仪研究了激光选区熔化和铸造成形TC4钛合金的微观组织演变及力学性能,进一步分析了不同成形条件下液态金属凝固冷却对其微观组织和力学性能的影响。结果表明:激光选区熔化与铸造成形的TC4钛合金分别为针状马氏体α′相的网篮组织、α+β相的魏氏组织。与铸造相比,激光选区熔化成形TC4钛合金具有极快的冷却速率(1.78×107℃·s-1)和较高的温度梯度,元素类型相同,晶体取向明显。同时,利用激光选区熔化(SLM)技术成形的TC4试样的抗拉强度、屈服强度、伸长率和硬度分别为1120.83 MPa、916.31 MPa、9.5%和123.04HV,而铸造试样的抗拉强度、屈服强度、伸长率和硬度分别为917.67 MPa、786.23 MPa、8.0%和77.876HV。与铸造成形相比,SLM成形的TC4试样的抗拉强度、屈服强度、伸长率和硬度增大,分别提升了22.14%、16.54%、18.75%和58%,因此激光选区熔化成形的TC4试样具有较好的力学性能。

With the help of finite element simulation,optical microscope(OM),scanning electron microscope(SEM),energy spectrum analysis(EDS),and Vickers hardness tester,the microstructure evolution and mechanical properties of TC4 titanium alloy by laser selective mel-ting and cast were studied.The effects of solidification and cooling of liquid metal on its microstructure and mechanics under different forming conditions were analyzed.The results show that laser selective melting and casting were basket structure of the needle-shaped martensiteα′phase and the Wei’s structure ofα+βphase.Compared with casting,the laser selective melting TC4 titanium alloy had an extremely fast cooling rate(1.78×107℃·s-1)and a large temperature gradient,with the same element type and obvious crystal orientation.Meanwhile,the tensile strength,yield strength,elongation and hardness of the TC4 specimens formed by SLM were 1120.83 MPa,916.31 MPa,9.5%and 123.04HV,while the tensile strength,yield strength,elongation and hardness of the TC4 specimens formed by casting were 917.67 MPa,786.23 MPa,8.0%and 77.876HV,compared with cast,the tensile strength,yield strength,elongation and hardness of TC4 specimens formed by SLM forming increased by 22.14%,16.54%,18.75%and 58%.Therefore,laser selective melting had better mechanical performance index.