Effect of heating treatment on the microstructural evolution and dynamic tensile properties of Ti-6Al-4V alloy produced by selective laser melting

In this paper, the influence of heating treatment on the microstructure and dynamic tensile properties of Ti-6Al-4 V alloy processed by selective laser melting (SLM) was systematically studied considering the influence of heating temperature. The microstructure of SLMed Ti-6Al-4 V consisted of nearly full acicular α’ martensite, and it decomposed into α + β phase after heating treatments, basket-wave and Widmanstatten morphologies were obtained with different heating temperature. Little change of texture intensity was detected in the as-built sample compared with heat-treated counterparts, moreover, dense LAGBs formed in the heat-treated samples, which will have great influence on the strength and ductility. As the heating temperature increased, the strength including ultimate tensile strength (UTS) and yield strength (YS) gradually decreased, the strain to fracture (εf) increased at first, then tended to drop once temperature exceeded the β transus (Tβ). Good balance of strength and ductility can be achieved with α + β treatment, sample treated at 925 °C had excellent UTS of 1114 MPa and εf of 15.4%, namely decreased by 17% and increased by 31% comparing with the as-built counterpart. Lots of interface phase was observed within the heat-treated samples, and in which dense deformation twins were observed after high strain rate tensile testing, thus led to good ductility by the twinning-induced plasticity mechanism.