Annealing of a magnesium alloy AZ31 after interrupted cold deformation

The isothermal annealing behaviors of a magnesium alloy AZ31, deformed by multi-directional forging (MDF) at ambient temperature to cumulative strains ranging from 0.2 to 1.5, was investigated at 473 K. The deformed microstructure is characterized by several types of twins formed in various directions during MDF and their intersections with one another. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) plots of Xrex-t curves are approximated by a linear relationship with an exponent of 2.6 at early stages of annealing irrespective of prior strains, but always break at long times, leading to lower values of the exponent. The non-linear JMAK plots may result from the inhomogeneity of deformed microstructures. The annealing process is composed of new grain formation at the intersections and subsequent large-distance migration of their boundaries, that is discontinuous static recrystallization (dSRX). The annealing characteristics of the cold-deformed Mg alloy are discussed comparing with the contrastive ones of the hot-deformed alloy.

► The AZ31Mg alloy is cold-deformed to strains up to 1.5 by multi-directional forging.
► The Mg alloy containing high-density twins and their intersections is isothermally annealed at 473 K.
► The annealing process can be controlled by discontinuous static recrystallization.