Evolution of the structure and strength of steel/vanadium alloy/steel hybrid material during severe plastic deformation

In the present study, severe plastic deformation (SPD) has been used to joint dissimilar materials and form a multilayer hybrid material with nano- and submicrocrystalline structure. The evolution of the structure and strength of steel/vanadium alloy/steel hybrid material during SPD by high-pressure torsion (HPT) has been studied. The HPT of three-layer metal block with from ¼ to 5 revolutions leads to the formation of firm joint of all layers. Deformation twists at steel/vanadium alloy boundaries are observed in the hybrid material subjected to HPT with the number of revolutions N=1. After HPT with N=5, the fragmentation of all vanadium alloy layer into thinner layers, which are rounded, vortex-like in shape, is observed. In this case, the microhradness of steel layers (measured at the sample midradius) increases by 3.2-3.5 times; the hardness of vanadium alloy layer increases by ~2.0 times.