SEM observations of grain boundary mobility under thermal and plasticity effects

Grain growth in high purity aluminum was studied by in situ experiments in a SEM in order to follow grain boundary mobility under thermal and plasticity effects. After a first cold rolling stage followed by a first heat treatment, samples are submitted to one or two sequences of 3% plastic strain followed by an additional heat treatment. SEM observations allow following the resulting mobility for representative sets of grain boundaries with either low or large misorientations between differently oriented grain pairs. This paper reports on the quantitative investigation of the driving force contributions due, on the one hand, to grain boundary curvatures as measured from experimental observations and, on the other hand, to differences of dislocation densities between the adjacent grains of each examined boundary, as estimated from numerical simulations of polycrystalline plasticity. A "migration diagram" representing these two contributions is presented and discussed with regard to existing velocity laws and models. (paper)