Dynamic recovery: sufficient mechanism in the hot deformation of Al (<99.99)

A recent OIM study of the substructure in hot compressed Al has observed an increase in the fraction of boundaries both of 15–20° and above 20° as strain rises from 0.9 to 1.5. This was interpreted as evidence of continuous dynamic recrystallization being the mechanism for the steady state deformation. However, when the original grain boundaries and transition boundaries between deformation bands are discounted, the fraction of 15–20° boundaries is reduced to less than 20% and would be much lower if subboundaries less than 0.5° visible in TEM were taken into account. The present authors argue that dynamic recovery maintains the subgrains of constant size, low misorientation and equiaxed to produce a steady state and can permit a limited number of discrete segments with higher misorientation notably as temperature falls. Moreover, continuous dynamic recrystallization is not appropriate terminology because it is far from reaching the completion observed in other instances of continuous recrystallization.