基于不同Mo添加的激光立体成形Ti-6Al-xMo合金的显微组织演化和力学性能

Microstructure Evolution Mechanism and Mechanical Properties of Laser Solid Formed Ti-6Al-xMo Alloys Based on Different Mo Additions

采用激光立体成形技术(laser solid forming,LSF),基于Mo当量混合Ti、Al、Mo粉末沉积新型Ti-6Al-x Mo(x=2,3,4)钛合金,研究了其显微组织形成与室温拉伸性能。结果表明:3种合金的凝固组织均呈现沿沉积方向生长的粗大柱状晶,顶部为细小等轴晶,且随着Mo含量的增加,柱状晶宽度逐渐减小,等轴晶层厚度逐渐增大;初生β晶粒中的微观结构是由初生α板条和残余β相组成的,还存在晶界α和α束域,通过EBSD分析发现3种成分均出现12种α变体且出现变体占优现象;随着Mo含量的增加,Ti-6Al-x Mo强度硬度增加,延伸率减小,初生α板条宽度和面积比减小,Mo含量(质量分数)增加到x=4时,晶内出现次生α相。相比之下激光立体成形的Ti-6Al-2Mo、Ti-6Al-3Mo合金分别具有抗拉强度962 MPa、延伸率11.5%和抗拉强度982 MPa、延伸率9.2%的优异室温拉伸性能。

Based on Mo equivalent design,novel Ti-6Al-x Mo(x=2,3,4)titanium alloys were deposited by laser solid forming(LSF)from mixed Ti,Al and Mo elemental powders,and the microstructure and tensile properties of the alloys were investigated at room temperature.The results show that the solidification microstructure of the three alloys presents coarse columnar grains growing along the direction of<100>,and the top is composed of equiaxed grains.With the increase of Mo content,the average width of the columnar grains decreases,and the thickness of the equiaxed grains layer increases gradually.The microstructure in primary β grains is composed of primary α lath and retainedβphase,and there also exists grain boundaryαandαcolonies.With the increase of Mo content,the width and area ratio of primary α lath decrease.When the Mo content increases to 4wt%,the secondaryαphase appears in the grain.Moreover,12 kinds ofαvariants are found in all the three components by EBSD analysis,and the variation is dominant.In terms of mechanical properties,the strength and hardness increase with the increase of Mo content while the elongation decreases.By contrast,Ti-6Al-2Mo and Ti-6Al-3Mo have the very good tensile properties with tensile strength of 962 MPa and elongation of 11.5%,and tensile strength of 982 MPa and elongation of 9.2%,respectively.