Equal channel angular pressing of Mg alloys; Processing, microstructure and mechanical properties

Equal channel angular pressing of difficult-to-work Mg alloys was conducted, and the pressing temperature that is one of most important processing factors in deformation of Mg alloys was established. Pure Mg and a commercial AZ91 Mg alloy were susceptible to shear localization during equal channel angular pressing; surface cracking occurred along to the direction of shear localization at lower temperatures than 573K. Uniform flow occurred at 573 K. In addition, 4 repetitive equal channel angular pressings of Mg were successfully conducted at 573K on the same sample that was rotated 180degrees around its longitudinal axis between pressings. The grain size of pure Mg was decreased from approximately 400 mum to 80 mum after 1 pressing at 573 K, and it remained almost unchanged after 4 pressings. The grains were dynamically recovered during the repetitive pressings at 573 K ( > 1/2Tm). A marked twinning was also observed in the equal channel angular pressed Mg. There was small increase of microhardness, proof stress and tensile strength in equal channel angular pressed Mg with no decrease in elongation.