Microstructure and texture characterization of superplastic Al-Mg-Li alloy

A novel thermomechanical processing was developed for producing fine grained Al-Mg-Li alloy sheets. The influences of static recrystallization annealing on the grain structure and superplastic behavior were investigated. The results show that the refined microstructure has a variation in the distribution of grain size, shape and texture across the normal direction of the sheet. The surface layer (SL) has fine, nearly equiaxed grains with a rotated cubeND {001}«310» orientation, whereas the center layer (CL) has coarse, elongated grains with a portion of α fiber orientation. Increasing static recrystallized temperature results in grain growth in the full thickness, decreasing of grain aspect ratio in the center layer, texture sharpening in the surface layer, but weakening in the center layer as well as decreasing of superplastic elongation. Increasing the annealing temperature also produces an sharpening of the rotated cube {001}«310» component and a decreasing of the α fiber texture in the full thickness of the sheet. The formation mechanisms of recrystallization texture at various temperatures and layers were discussed.