Experimental verification of grain boundary-sliding controlled steady state superplastic flow in both continually and statically recrystallizing Al alloys

The complex microstructural changes following superplastic deformation in statically and continually recrystallizing Al-alloys are examined. Al alloy, AA 2004, exhibits continual recrystallization during deformation, whereas in two other alloys, AA 5456 and AA 7020, static recrystallization leads to the formation of equiaxed grains prior to the onset of superplastic deformation. Other features such as grain growth, grain rotation, dislocation accumulation and their influence on texture evolution during superplastic deformation are investigated. The observations clearly suggest that grain boundary sliding is the rate controlling process during steady state superplastic deformation.