Effect of electric pulse treatment on the structure and hardness of nickel deformed at room and liquid nitrogen temperatures

Abstract

Abstract The influence of the energy of electro-pulse processing (EPP) on the structure and hardness of pure nickel deformed at room and liquid nitrogen temperatures is studied. The metal was subjected to isothermal rolling with a strain of 90% and subsequent EPP with integral current densities Kj in the range from 0.06 to 0.19×105 A2s/mm4 corresponding to the calculated temperature range of 130-925°C. It was found that decreasing the rolling temperature of Ni resulted in a more uniform and less misoriented nanocellular structure and a 15-20 HV higher hardness. Subsequent EPP decreased the hardness due to recovery, discontinuous recrystallization with the formation of annealed twins and growth of new grains. It is revealed that a more uniform fine-grained structure with a smaller grain size is formed in the cryorolled metal in a narrower interval and at less EPP energies.