Reversion and Reaging in an Al-2at%Zn-2at%Mg Alloy

Abstract

Kinetics of reversion and reaging of an Al-2at%Zn-2at%Mg alloy have been studied by resistivity measurements and tensile tests. Perfect reversion occurred only when aged at 20°C. The formation of the transition phase was found to occur in parallel with the dissolution of zones when the specimen aged at 70°C was reverted at 200°C. An incubation period accompanied with initial fast and slow reactions was observed in reaging. When the aging prior to reversion was ceased before the end of fast reaction, the incubation period was not observed, similarly in the case of Al-Cu alloy. It will be clear that the nucleation is necessary for zone formation in Al-Zn-Mg alloys. The initial fast and slow reactions will be explained in terms of the amount of vacancies compared with the number of solute atoms after reversion.