Directional annealing of cold-rolled copper single crystals

Abstract

The effects of annealing temperature, hot zone velocity and temperature gradient ahead of the hot zone on the microstructure of directionally-annealed, cold-rolled, high-purity copper single crystals were investigated. Columnar grains were observed at an optimum hot zone velocity that increased with increasing annealing temperature and decreasing temperature gradient. Equiaxed grains were formed both when the velocity of hot zone movement was low, and when it exceeded the maximum growth rate of grains. The number of twin boundaries per unit area decreased with increasing hot zone velocity, increasing temperature gradient and decreasing annealing temperature. The results are explained in terms of the effects of annealing temperature and temperature gradient on the grain boundary mobility and the nucleation of new grains and twins.