激光选区熔化TC4钛合金高温力学性能和显微组织研究

High Temperature Mechanical Properties and Microstructure of TC4 Titanium Alloy Prepared by Selective Laser Melting

采用万能拉伸试验机以及光学显微镜、扫描电子显微镜和透射电子显微镜等测试技术,研究了室温至550℃温度范围内激光选区熔化(SLM)成形TC4钛合金的力学性能和显微组织。结果表明:SLM成形TC4钛合金由针状马氏体α′相组成,晶界数量多,塑性变形时位错运动被限制在马氏体内部,因此试验合金具有高强度,室温抗拉强度为1 265 MPa,500℃抗拉强度为834 MPa,优于固溶时效处理和退火处理的TC4钛合金,然而,在500℃以上拉伸变形时,马氏体逐渐转变为平衡态的α相,组织形态由针状向片层状转变,晶界数量减少,材料抗变形能力下降,因此抗拉强度快速降低,550℃抗拉强度只有562MPa。

In this paper,the mechanical properties and microstructure of TC4 titanium alloy,prepared by selective laser melting(SLM),at room temperature(RT)to 550℃were studied by universal tensile testing machine,optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the TC4 alloy produced by SLM consists of acicularα′martensite with a large number of grain boundaries,and the dislocation movement is limited to the interior of martensite during plastic deformation.Therefore,the experimental alloy has a high strength,with a tensile strength of 1265 and 834 MPa at RT and 500℃respectively,which is better than that of the TC4 alloy separately by solid solution aging treatment and anneal treatment.However,when it is deformed at temperatures above 500℃,martensite gradually transforms into equilibriumαphase,and the morphology changes from acicular to lamellar structure.The decrease in the number of grain boundaries leads to a decrease in deformation resistance,so the tensile strength decreases rapidly to 562 MPa at 550℃.