Ostwald ripening and stability of precipitates during two successive overaging in an Al-Mg-Li alloy

Abstract The precipitate coarsening and dissolution behaviors in an Al-Mg-Li alloy during overaging at 300°C and then at 400°C for various time were investigated. It is shown that the S1-phase tends to have rod-shaped morphology upon overaging at 300°C. However, followed by overaging at 400°C, which is the dissolution temperature for S1-phase, the rod-shaped S1-phase precipitates formed previously were not dissolved until their coarsening were finished. The ensuing reduction of the total precipitate–matrix interface energy due to the dissolution of small precipitates and spheroidization of the rod-shaped precipitates was suggested to provide the driving force for coarsening.