Combined effects of grain size and recrystallization on the tensile properties of cryorolled pure vanadium

The effects of grain size and recrystallization on the tensile behavior of cryorolled pure vanadium were investigated. During equal channel angular pressing, the grain size was reduced from 100 μm to 0.2 μm in lamellar thickness; it was further reduced to 0.14 μm by an additional 60% cryorolling. The grain refinement was accompanied by enhancing the yield strength by 30%. Upon annealing, the cryorolled vanadium showed a gradual decrease of yield strength with increasing grain size, in accordance with the Hall–Petch (H–P) relation. The yield strengths of the unrecrystallized vanadium, however, were higher by about 50 MPa, than those expected by extrapolation of the Hall–Petch relation determined from the recrystallized samples. In the recrystallized condition, the tensile ductility of vanadium decreased gradually with a decrease in grain size to 1 μm, but further reduction in grain size had little influence on ductility. The insensitivity of ductility to the grain size below 1 μm apparently resulted from the counter-balancing effects of the reduced hardening capacity and increased hardening sources.