Structural development at severely high strain in AZ31 magnesium alloy processed by cold forging and subsequent annealing

The microstructural development in a AZ31 magnesium alloy during cold multi-directional forging followed by annealing is investigated in a wide range of cumulative strains up to 5. The kinetics of recrystallization is accelerated accompanying with increase in the Johnson–Mehl–Avrami–Kolmogorov slope from 2.6 to 4.7 as well as an appearance of a linear Johnson–Mehl–Avrami–Kolmogorov relationship. The grain size evolved after annealing decreases with repeated multi-directional forging and approaches around 1 μm in high strain. A strong initial texture is broken gradually with repeated multi-directional forging and almost disappears at severe high strain of 5. These can be because various variants of deformation twins and their intersections introduced by multi-directional forging are homogeneously developed in high density by repeated changing of the loading directions during multi-directional forging. The annealing process and the mechanisms occurring after cold multi-directional forging are discussed comparing with those after hot multi-directional forging.