The microstructure and mechanical properties of laser beam welded dissimilar joints in TC4 and TA15 titanium alloys were investigated. The results showed that the coarse columnar grains containing a large amount of acicular α and martensite α′ were present in the fusion zone (FZ), some residual α phases and martensite structure were formed in the heat-affected zone (HAZ) on TC4 side, and bulk equiaxed α phase of the HAZ was on TA15 side. An asymmetrical microhardness profile across the dissimilar joint was observed with the highest microhardness in the FZ and the lowest microhardness in TA15 BM. The orders of yield strength and ultimate tensile strength were as follows: TC4 BM > TC4/TC4 similar joint > TA15 BM > TA15/TA15 similar joint > TC4/TA15 dissimilar joint, and increased while hardening capacity and strain hardening exponent decreased with increasing strain rate from 1×10−4 s−1 to 1×10−2 s−1. The TC4/TA15 dissimilar joints failed in the TA15 BM, and had characteristics of ductile fracture at different strain rates.%研究 TC4/TA15异质钛合金激光焊焊缝的显微组织和力学性能。结果表明：TC4/TA15异质钛合金激光焊缝熔合区显微组织由针状α相和马氏体α′组成，TC4侧热影响区主要是残余α相和马氏体α′，TA15侧热影响区则出现了大量等轴α相。焊缝显微硬度呈现不对称特征，熔合区最高，TA15母材区最低。随应变速率由1×10−4 s−1增加到1×10−2 s−1，接头屈服强度和抗拉强度均升高，且满足 TC4母材>TC4/TC4同质接头>TA15母材>TA15/TA15同质接头>TC4/TA15异质接头，而硬化能力和应变硬化指数则降低。不同应变速率下拉伸 TC4/TA15异质接头均在 TA15母材断裂，断口呈现韧性断裂特征。
展开▼
