The effect of a fine particle dispersion on heterogeneous recrystallization

Abstract

The recrystallization behaviour of an AlMn alloy containing a duplex particle structure consisting of a coarse distribution of large cast in inclusions and a finer dispersion of smaller particles due to precipitation prior to recrystallization has been investigated. For a wide range in the fine particle dispersion level, it has been established that the recrystallization reaction is quasi site saturated. A model describing this type of grain nucleation has been constructed based on the assumption that the finely dispersed particles restrict subgrain growth to grains of larger than average size. By assuming that only these subgrains contribute in the heterogeneous grain nucleation process and by selecting these grains analogous to that of the well-known analysis of abnormal grain growth, an expression has been derived which relates the number of grain nucleation events (nucleation rate) to the particle dispersion and subgrain size distribution. It is further demonstrated that this model is capable of accounting for the experimentally determined relationships between the recrystallized grain size and particle dispersion in the specimens prior to recrystallization.