Structure and hardness of B2 ordered refractory AlNbTiVZr0.5 high entropy alloy after high-pressure torsion

High-pressure torsion (HPT) at room temperature was applied to an AlNbTiVZr0.5 refractory high entropy alloy. In the initial as-cast condition the alloy was composed of a coarse-grained B2 matrix phase and a continuous network of C14 Laves phase particles with the volume fraction of 19%. HPT resulted in the formation of a nanocrystalline structure in the B2 matrix with an average size of grains/subgrains of 25 nm after 5 revolutions. The B2 phase also underwent significant disordering during HPT. The Laves phase network was broken and individual particles became much thinner in comparison with those in the initial condition. Microhardness measurements have revealed typical of HPT gradient along the radius which decreased with increasing the number of revolutions. It was also found that the nanohardness of the B2 phase increased after HPT while the nanohardness of the Laves phase decreased. A strong decrease in the Young's modulus of the B2 phase was also found. Factors governing structure and properties evolution of the alloy during HPT were discussed.