The recrystallization behavior of materials containing a wide distribution of particle sizes can be difficult to predict. This is compounded in alloys where the particles are thermally-unstable and may grow or dissolve with time. In various systems, abnormal grain growth may occur giving rise to unusually large crystallites growing at the expense of smaller ones. The situation is more simple in bimodal alloys which have two distinct particle populations. An example is Al-Si alloys where it has been shown that even in the presence of very large (<5 μm) particles the recrystallization behavior is dominated by the small particles (Chan & Humphreys 1984). In such cases the resulting microstructure tends to resemble one from an alloy with only small particles.