The Classification and Determination of Restoration Mechanisms in the Hot Working of Al Alloys

Abstract

Dynamic recovery (DRV) and recrystallization (DRX) are softening mechanisms that have distinctive effects on shaping the flow curve and retarding fissure formation to raise the hot ductility. DRV alone produces equiaxed subgrains in elongated original grains, whereas DRX gives rise to equiaxed grains containing a DRV substructure resulting from deformation during DRX. Confusion arises at very high strains (> 10) when the elongated grain thickness is almost equal to the subgrain diameter. As a result of strong serrations in the original boundaries, one third of the perimeter of the average subgrain has a high misorientation. Moreover, serrations protruding into grains from above or below the observation plane may give the appearance of nuclei. The microscopic procedures for distinguishing DRV from DRX are discussed. Reinterpretation is made of several published results to show that DRX does not take place in Al alloys having less than 4% Mg. (orig.).