激光选区熔化Ti6Al4V的工艺参数优化与显微组织

Study on processparameter optimization and microstructure of Ti6Al4V prepared by selective laser melting

采用激光选区熔化技术制备Ti6Al4V钛合金试样,研究了激光加工工艺参数对Ti6Al4V试样致密化行为、显微组织特征及力学性能的影响。利用金相显微镜、万能试验机等测试手段对激光选区熔化成形试样进行显微组织及综合力学性能分析。结果表明,随着激光功率由360 W提高到400 W,不同激光扫描速度下的试样平均致密度由85.3%提高到94.5%,致密度显著提高。随激光能量密度提高,孔隙率明显降低且针状马氏体α′相分布均匀,塑性和强度更好。选用最优工艺参数(功率400 W,扫描速度2100 mm/s),试样抗拉强度为1159 MPa,屈服强度为1008 MPa,均高于锻件标准。经800℃保温2 h退火处理后,断后伸长率和断面收缩率分别提高2.26倍和2.68倍,增长幅度较大。α′相和β相均分解为α+β相,晶粒粗化使晶粒内部滑移变形受晶界抑制作用减弱,最终导致材料强度下降而塑性明显提高。

Ti6Al4V test specimens were prepared by selective laser melting(SLM).Influence of laser process parameter on densification behavior,microstructure and mechanical properties of Ti6Al4V alloy specimens was researched.Microstructure and comprehensive mechanical properties of SLM formed samples were analyzed by metallographic microscope and tensile testing machine and other test methods.The result showed that the average density of the sample at different laser scanning speeds increased from 85.3%to 94.5%with the laser power increasing from 360 W to 400 W,and the density increased significantly.As the laser energy density increased,the porosity decreased significantly and the acicular martensiteα′phase with better plasticity and strength distributed uniformly.Using the optimum process parameter(P=400 W,v=2100 mm/s),the tensile strength and yield strength of the specimens were 1159 MPa and 1008 MPa,respectively,which were higher than the forging standard.After annealing at 800℃for 2 h,the elongation and reduction of area increased by 2.26 tiems and 2.68 times,respectively,with a large increase.Bothα′andβphases transformed intoα+βphase,and grain coarsening weakened the grain boundary inhibition effect of internal slip deformation,which resulted in the material strength decreasing and its plasticity increasing remarkably.