Effect of composition, annealing temperature, and high pressure torsion on structure and hardness of Ti–V and Ti–V–Al alloys

Abstract

The severe plastic deformation strongly changes the microstructure and properties of titanium-based alloys. The structure and microhardness of four binary and ternary titanium-based alloys (Ti–4 wt. % V, Ti–4 wt. % V–6 wt. % Al, Ti–4 wt. % V–3 wt. % Al, and Ti–5 wt. % V–6 wt. % Al) have been studied after preliminary annealing and following high pressure torsion (HPT). After HPT, the Ti–4 wt. % V alloy contains much less (ωTi) phase than Ti–4 wt. % Fe and Ti–4 wt. % Co alloys. The addition of aluminum to the binary Ti–V alloys completely suppresses the formation of the high-pressure (ωTi)-phase. HPT leads to the partial decomposition of the annealed (αTi) solid solution and “purification” of α-phase similar to that in the Ti–Fe alloys. After HPT of the studied ternary alloys, the (βTi)-phase completely disappears and nanoparticles of Ti2Fe form instead. This fact explains why the addition of aluminum leads to the increase of microhardness of alloys after annealing between 600 °C and 950 °C and after HPT-treatment. The increase of the temperature of the preliminary annealing also increases the hardness of all alloys after HPT-treatment.