Mesoscale simulations of particle pinning

Abstract

Abstract Despite much debate, there is still little consensus of opinion on the dependence of Zener pinning (the stagnation of grain growth caused by second-phase particles) on the volume fraction. The controversy surrounds attempts to relate the volume fraction of particles to the final pinned grain size. Analytical theories and 3D Monte Carlo simulations are in disagreement and the experimental evidence is inconclusive. In this paper we contribute to the debate by describing mesoscale 3D Monte Carlo simulations of a single boundary moving through an array of particles. It is found that the simulation temperature is a critical variable, and the simulated boundaries possess mobilities independent of driving force only when kT′ ≥ 2. This is explained in terms of a ledge mechanism of migration in which ledge repulsion becomes important when kT′ < 2. The effect of T′ is critical in determining the geometry of the boundary (and hence the pinning force) during particle bypass. When kT′ = 0, the expected dimple shape is not observed because the boundary is in a non-equilibrium state (due to ledge repulsion) and this is the origin of the strong pinning observed in the simulations. When kT′ ≥ 1. dimples are observed and the pinning force is in good agreement with analytical theory. The implications of this work on the volume fraction dependence of Zener pinning are discussed.