In-situ annealing experiments of octachloropropane as a rock analogue: kinetics and energetics of grain growth

Two-dimensional in-situ observation of the change of size of individual gra ins of octachloropropane (OCP) during post-deformation annealing revealed t hat grain boundary migration occurred to reduce the grain boundary energy. Within the polycrystalline aggregate studied some grains show a cyclic chan ge in grain size, others have a stable grain size, while most grains were c onsumed and disappeared in order that the mean grain size could increase. D uring grain coarsening, some grains were dissected, then coalesced, amalgam ated with others and their centers migrated across the aggregate. The avera ge grain size ((D) over bar) can be expressed by (D) over bar = k(0) exp(- Q/RT)t(n), where k(0) is a constant, Q is the activation energy, R is the g as constant, T is the temperature, t is the annealing time and n is a const ant. We obtained n = 0.1-0.2 and Q = 6.2 kcal/mol. The driving force (P) is the surface energy stored at grain boundaries. The driving force can be ex pressed as P proportional to t(m), where m is the constant, and hence the g rain growth rate (<(D')over bar>) can be expressed as <(D')over bar> propor tional to P(n - 1/m). The value of (n - 1)/m ranges from 4 to 10. (C) 1999 Elsevier Science B.V. All rights reserved.