MICROTEXTURE INVESTIGATION OF THE RELATIONSHIP BETWEEN STRAIN AND ANOMALOUS GRAIN-GROWTH

Strain-induced anomalous grain growth has been investigated in pure nickel. It was found that slow heating to a holding temperature of 1000-degrees-C greatly increased the proportion of anomalous growth compared with isothermal annealing at 1000-degrees-C. There were also differences in the misorientation distributions of the two specimens, although the main feature of both was that the majority of boundaries were high-mobility types. Mechanisms for strain-induced grain growth are discussed, both in terms of the present data and in a wider context. It is suggested that the often observed 'grain growth incubation period' is in fact a grain-boundary recovery stage when boundaries are able to rearrange towards connected groups having a lower energy and/or higher mobility. This in turn increases the selectivity of sites for the initiation of grain growth and hence the degree of anomalous grain growth.