DEFECT STRUCTURE OF NIOBIUM SINGLE CRYSTALS DEFORMED BY ROLLING AT 77 degree K.

The methods of electron microscopy, electrical resistance and microhardness were used to study niobium single crystals rolled at 77 degree K with two different orientations, (001) left bracket 110 right bracket and (112) left bracket 201 right bracket . The changes in the defect structure of the single crystals are found to occur mainly at the initial stage of deformation (as far as delta equals 20%), with dynamic equilibrium being established between the processes of hardening and softening at higher levels of deformation. Rolling causes more turbulent flow in (112) left bracket 201 bar right bracket than (001) left bracket 110 right bracket single crystals, and this results in a greater tendency for recrystallization. (112) left bracket 201bar right bracket crystals are softened mainly at the stage of recrystallization in situ during annealing.