Dynamic strain localization in magnesium alloy AZ31B-O

The high strain-rate behavior of annealed AZ31B-O magnesium alloy is explored using an electromagnetically driven expanding ring experiment. Two variants are considered, one in which the magnesium specimen is heated by the Joule effect as it carries a large current, and another in which a copper pusher ring is used to carry the current, leaving the magnesium specimen unheated. The results indicate that the onset of dynamic strain localization is not influenced significantly by the strain-rate or the Joule heating. The initial expansion is interpreted in terms of a simple one dimensional model of ring expansion; this indicates that a power-law strain hardening model can describe the material response adequately. The formation of fragments is analyzed subsequently using Mott's probabilistic model for fragmentation as well as through direct numerical simulations. It is found that the left tail of the flaw distribution is the most important part in dictating the formation of fragments.