Effect of pre-annealing on the formation of the ω -phase in the Ti-2 wt%V alloy after high-pressure torsion

Although vanadium is used in many alloys as an alloying element, the binary Ti–V system has been studied very poorly. In particular, the effect of heat treatment in combination with high-pressure torsion (HPT) has not been studied at all for this system. The Ti-2 wt%V alloy was pre-annealed at three temperatures in two different regions of the Ti–V phase diagram, namely at 400 °C ( α phase), 700 °C ( α phase) and 1000 °C ( β phase). The as-cast state was also investigated. After annealing and quenching, all four samples contained only the α / α ′ phase. After the HPT, the ω -phase appeared in the material. Its portion increased from 70 to 76% with an increase in the pre-annealing temperature, but the as-cast sample had after HPT the largest proportion of ω Ti phase of 86%. The values of nanohardness ( H ) and Young’s modulus ( E ) after HPT were measured. H increased from 5.1 ± 0.1 to 6.4 ± 0.1 GPa with increasing pre-annealing temperature. The steady-state value of torsion torque during HPT also increases from 1533 to 2094 N m. However, the E value remained almost unchanged at 147 ± 3 GPa. The microhardness of the samples after HPT increased by about two times compared to the annealed samples.