Effect of Solution Treatment and Short Time Aging on Mechanical Properties of Cast Ti-6Al-4V Alloy

The effect of heat treatment on the microstructure and mechanical properties of cast Ti-6%Al-4% V alloy was investigated. Heat treatment of cast Ti-6Al-4V alloy was conducted by solution treatment at 950 degrees C for 30 min; this was followed by water quenching and then aging at 550 degrees C for 1 to 1440 min. The highest hardness of the heat-treated specimens was obtained by solution treatment and subsequent aging for 5 min due to precipitates of fine a that formed from retained beta phase. The tensile strength of this alloy increased without dramatic decrease of the ductility due to microstructural refinement resulting from the decomposition of alpha' martensite into fine alpha and beta phases, and also due to the fine alpha phase formed from the retained beta phase by aging treatment for 5 min. In addition, this strengthening might be caused by the transformation induced plasticity (TRIP) effect, which is a strain-induced martensite transformation from the retained beta phase during deformation, and which occurs even after aging treatment at 550 degrees C for 5 min.