Secondary recrystallization by grain boundary unsewing in Al-1wt-%Mg 2 Si alloy

Abstract

The interaction between grain growth and precipitation in a slightly supersaturated AI-1 wt-% Mg₂Si alloy has been investigated. After a short recrystallization anneal in the solid-solution region the samples were quenched in water at room temperature. This introduced quench-nucleated precipitates exclusively at the grain boundaries when subsequent annealing was carried out a few degrees below the solvus temperature. Normal grain growth was impeded by the particles and, after an incubation time that depended strongly upon temperature, a few abnormal grains developed. The grain boundaries of these grains were free from particles and they grew rapidly until the whole specimen was consumed. The old matrix structure could be recognized in the interior of the abnormal grains as it was outlined by a particle network. A qualitative model for the nucleation process based on Hillert's theory for grain growth and the Zener drag is suggested.