INFLUENCE OF A FINE PARTICLE DISPERSION ON THE RECRYSTALLIZATION BEHAVIOUR OF A TWO PHASE ALUMINIUM ALLOY.

A characteristic of the recrystallization behavior of supersaturated Al-Mn alloys is the development of abnormally large grain sizes when recrystallization takes place at low temperatures. Plotting of TTT diagrams for the decomposition and the recrystallization reactions of an Al-0. 9Mn-0. 35Fe alloy indicates that the abnormal grain size phenomenon is confined to cases where precipitation starts prior to the nucleation of new grains. That the heterogeneous grain nucleation process is site saturated, and that the amount of Mn precipitated prior to the formation of new grains has a bearing on the number of nucleation events. This effect is described in terms of a qualitative model relating the grain nucleation to the interaction between the fine dispersion of precipitate particles and the recovering subgrain structure.