Rekristallisationsverhalten von zonengeschmolzenem nickel

Abstract

The process of primary recrystallization and the subsequent grain growth were investigated in high purity zone melted nickel after 60 and 80% cold work.The formation of nuclei occurred predominantly at original grain boundaries by growth of subgrains which had already been formed during the deformation process.The rate of grain growth during and after primary recrystallization was determined by observing the time dependence of the largest and of the average grain diameters. The results may be interpreted in terms of the concept that the elementary process of grain boundary motion consists of a diffusion of single atoms across the grain boundary. Then the rate determining process is the grain boundary diffusion. The activation energy of grain growth was about 28–30 kcal/Mol and was equal to the activation energy of nuclei formation for large degrees of deformation.During the primary recrystallization the time dependence of the isothermally recrystallized fraction XR of the matrix may be described by the equation xr = 1 − exp(−Btκ). The K-value of 1.38 suggests a predominantly one-dimensional grain growth.The experimental data for the rate of grain growth after primary recrystallization indicate an influence of residual impurities still present in the crystal.