退火温度对激光选区熔化成形TC4钛合金组织及力学性能的影响

Effect of annealing temperature on microstructure and mechanical properties of TC4 titanium alloy formed by selective laser melting

采用激光选区熔化技术(SLM)制备TC4钛合金,借助光学显微镜、扫描电镜和万能材料试验机等测试手段,研究了退火温度对TC4钛合金显微组织和力学性能的影响。结果表明:SLM成形TC4样品横截面组织主要由六边形网格分布的等轴晶组成,纵截面主要由外延生长的柱状晶组成,晶粒内部包含大量针状马氏体α’相;随着退火温度的升高,组织内针状马氏体α’相发生分解,α相、β相开始聚集长大,退火温度800℃以上时,组织由魏氏体组织向网篮组织转变;随着退火温度的升高,合金的力学性能宏观呈现强度下降,伸长率上升的规律。综合比较几种退火制度发现,800℃×2 h/FC处理后的TC4合金获得相对最佳的综合力学性能。

TC4 titanium alloy was prepared by selective laser melting technique(SLM),the effect of annealing temperature on microstructure and mechanical properties of TC4 titanium alloy was studied by means of optical microscope,scanning electron microscope and universal material testing machine.The results show that the cross section of the TC4 samples is mainly composed of hexagonal equiaxed crystals,the longitudinal sections are mainly composed of epitaxial columnar crystals,and a large number of acicular martensiteα’phases are found in the grains.With the increase of annealing temperature,theα’phase of acicular martensite begins to decompose,theαphase andβphase begin to gather and grow.When the temperature is above 800℃,the whole microstructure begins to change from widmanstatten structure to net-basket structure;with the increase of annealing temperature,the mechanical properties of the alloy show the law of decreasing strength and increasing elongation.By comparing several annealing systems,it is found that the TC4 alloy treated at 800℃×2 h/FC will obtain the best comprehensive mechanical properties.