ON THE KINETICS OF SHRINKING GRAINS

Photoemission microscopy is used to observe grain boundary migrating during grain growth in a Ti-6Al-2V-2Zr (wt%) alloy. Analysis of the motion of the grain boundary/edge intercepts with the free surface is performed on disappearing grains. These grains exhibit parabolic shrinkage kinetics of the form [L]2(t)-[L]2(0) = -Ct. The characteristic length [L](t) is defined as the geometric mean edge spacing of the grain at the free surface at time t, and C is a positive constant that depends on the topology and shape of the grain below the free surface. The significance of these results with respect to grain growth is discussed.