Effect of Grain Structure on the Mechanical Properties of Al-Zn-Mg-Sc Alloys with T6 State

Al-Zn-Mg-Sc alloys with different grain structures were fabricated using friction stir processing (FSP) and rolling with different routes. The hot rolling (HR) sample after T6 treatment exhibited stronger <111> texture than the other three samples, and the T6 FSP samples exhibited the finest grains, with average grain size (AGS) of 5 μm. Cold or hot rolling before T6 treatment led to grain coarsening in the T6 FSP samples, and the AGS in the T6 FSP + HR reached 126 μm. All the samples exhibited a low density of dislocations and contained coarse grain boundary precipitates, Al₃(Sc,Zr) phases, and a high density of η′ phase. The T6 HR sample exhibited the highest strength mainly due to its strong <111> texture and reasonable grains size, and the T6 FSP sample exhibited the highest ductility due to its fine equiaxed grain structure, which can promote the redistribution of stresses and prevent strain localization during the tension process.