Microstructure evolution and strengthening mechanism of electron beam welded TiBw/Ti6Al4V composite joint

Abstract The microstructure and mechanical properties of the 3.5 vol% TiBw/Ti6Al4V composite electron beam welded joint was investigated in this paper. The microstructure evolution during the cooling stage was anatomized. Microhardness and tensile strength were used to evaluate the mechanical performance. Results showed that a novel micro-network reinforcement distribution was constructed in the weld zone with a basket-weave microstructure of the matrix. The weld zone was composed of α-Ti, β-Ti, and TiB whiskers. Solid-state phase transformations, α phase to β phase and β phase to α’ phase were observed in the heat-affected zone. The microhardness value of the weld zone was almost uniformly distributed with an average value of 438 HV, which was higher than that of the heat-affected zone and base metal. The ultimate tensile strength of the joint could reach 96% (room temperature) and 94% (600 °C) of the base metal, respectively.