Cooling Rate Effect on Microstructures and Mechanical Properties of Ti-7Al-1Mo-0.5V-0.1C

The Ti-7Al-1Mo-0.5V-0.1C alloy exhibits low density and good mechanical properties, and has potential applications in aerospace industries. The microstructure features of titanium alloys, such as the morphology and volume fraction of the primary α phase (α _p) and the precipitation of the secondary α phase (α _s), are sensitive to heat treatment parameters, especially the cooling rate from the two-phase region. In this work, we have characterized the precipitation of the secondary α phase and ordered α ₂ phase in Ti-7Al-1Mo-0.5V-0.1C alloy under water quenching, air cooling, and furnace cooling, and have investigated their effects on the mechanical properties of the Ti-7Al-1Mo-0.5V-0.1C alloy. The results show that the secondary α phase is significantly coarsened in the air-cooled alloy and leads to an increase in the strength but decrease in the ductility of the alloy, while the equiaxed microstructure generated in the furnace-cooled alloy, with no precipitation of the secondary α phase and an increase in size of the ordered α ₂ precipitation phase within the primary α phase, contributes to a further increase in ductility.