基于团簇成分式设计激光增材制造Ti−Al−V−Nb系合金的显微组织与力学性能

Microstructures and mechanical properties of Ti−Al−V−Nb alloys with cluster formula manufactured by laser additive manufacturing

基于Ti−6Al−4V合金团簇成分式,用Nb替代团簇式中的V设计Ti−Al−V−Nb系合金,其团簇成分式为12[Al−Ti_(12)](AlTi_(2))+5[Al−Ti1_(4)](V,Nb)_(2)Ti。采用激光增材制造技术制备不同Nb含量(0~6.96%Nb,质量分数)合金的单道熔覆层和块状试样,并对其成形性、显微组织和力学性能进行研究。结果表明,Nb可以增加单道熔覆层的表面粗糙度,降低熔池高度,从而改善合金的铺展性。Ti−5.96Al−1.94V−3.54Nb(质量分数,%)合金由于熔池高度与预设沉积层厚度一致,表现出优异的几何精度。Ti−Al−V−Nb系合金块体样品的组织由沿沉积方向外延生长的β柱状晶构成,而β柱状晶内为α板条构成的网篮组织。随着Nb含量的增加,α板条的宽度增加,而其尺寸均匀性降低。合金的维氏硬度沿沉积方向度逐渐增加。由于α板条宽度和含量具有较好的匹配关系,所以Ti−5.96Al−1.94V−3.54Nb合金具有最高的维氏硬度。

Ti−Al−V−Nb alloys with the cluster formula,12[Al−Ti_(12)](AlTi_(2))+5[Al−Ti1_(4)](V,Nb)2Ti,were designed by replacing V with Nb based on the Ti−6Al−4V alloy.Single-track cladding layers and bulk samples of the alloys with Nb contents ranging from 0 to 6.96 wt.%were prepared by laser additive manufacturing to examine their formability,microstructure,and mechanical properties.For single-track cladding layers,the addition of Nb increased the surface roughness slightly and decreased the molten pool height to improve its spreadability.The alloy,Ti−5.96Al−1.94V−3.54Nb(wt.%),exhibited better geometrical accuracy than the other alloys because its molten pool height was consistent with the spread layer thickness of the powder.The microstructures of the bulk samples contained similar columnar β-phase grains,regardless of Nb content.These grains grew epitaxially from the Ti substrate along the deposition direction,with basket-weaveα-phase laths within the columnar grains.Theα-phase size increased with increasing Nb contents,but its uniformity decreased.Along the deposition direction,the Vickers hardness increased from the substrate to the surface.The Ti−5.96Al−1.94V−3.54Nb alloy exhibited the highest Vickers hardness regardless of deposition position because of the optimal matching relationship between theα-phase size and its content among the designed alloys.