EFFECT OF ELECTRIC PULSING ON THE STRUCTURE, TEXTURE AND HARDNESS OF CRYOROLLED FINE-GRAIN COPPER

A synergy effect of cryorolling and high-dense electric pulsing on the structure, texture and hardness of fine-grain Cu is analyzed. More than twice Cu strengthening under rolling with 90% reduction at –196°С was caused by strong rolling texture and work-hardened nanostructure with ~300 nm crystallites and ~30% fraction of high-angle boundaries. Further single pulsing with current intensity Kj = 3.5×104 A2s/mm4 resulted in a static recovery and slight Cu softening due to the formation of a more equilibrium structure with lower dislocation density and lattice microstrain. Increasing Kj to 3.8×104 A2s/mm4 led to a sharp drop in the Cu hardness owing to continuous recrystallization and texture randomization. At Kj near 5.0×104 A2s/mm4 homogeneous ultrafine-grain structure with 1 μm defect free equiaxed grains and about 30% of twin boundaries is formed. Normal grain growth to 3 µm and gradual decrease of the Cu hardness were taking place at higher pulsing energies, up to 8.1×104 A2s/mm4.