Microstructure and mechanical properties of MIG welded joint of laser melting deposited TA15 titanium alloy

Laser melting deposited (LMD) TA15 and rolled TA15 were welded by argon arc welding. The microstructure and phase constitution of the welded joint were studied by optical microscopy and scanning electron microscopy. The microhardness and mechanical properties of the welded joint were tested. The results indicate that the weld zone (WZ) mainly consists of columnar crystals with thick lamellar structure which epitaxially grow from the substrates. The grains in heat affected zone (HAZ) of rolled TA15 grow seriously because of its sensitivity to heat. The columnar grains in HAZ near weld zone of LMD TA15 turn into equiaxial grains. The microhardness of HAZ of LMD TA15 is the highest, while the WZ and HAZ of rolled TA15 is the lowest. The tensile strength of the welded joint is lower than that of both base metals, but the plasticity corresponds to the rolled TA15. Fracture position locates in the HAZ of rolled TA15.