Effect of temperature of HPT deformation and the initial orientation on the structural evolution in single-crystal niobium

Abstract

The structural evolution and hardness of sing-crystal niobium with various initial orientations are investigated after its deformation in Bridgman anvils at room (290 K) and cryogenic (80 K) temperatures. It is shown that no twinning occurs upon cryogenic deformation; thin prolonged bands dividing the matrix into weakly misoriented regions are formed. The uniform-in-size structure of a nanoscale level (d_av = 40 nm) is formed during cryogenic deformation after the maximum achieved true strain. The average microcrystallite size observed after room-temperature deformation is 120 nm.