Anelasticity of die-cast magnesium-aluminium based alloys under different strain rates

Cyclic tension loading-unloading tests were conducted over a wide quasi-static strain rate range 10(-6) - 10(-1) s(-1) on a variety of die-cast Mg-Al based alloys, from which the deformation behaviour, especially the anelasticity, has been systematically studied. At the early stages of deformation, prior to the onset of extensive prismatic slip, the anelastic strain is less dependent on strain rate but varies between the alloys. Upon the activation of extensive prismatic slip, the anelastic strain starts to saturate at a maximum. The maximum increases with increasing strain rate and varies between alloys. The strain-rate dependence of the maximum an elastic strain can be interpreted in terms of solid solution softening/hardening of slip planes and their influence on twinning. Implications of the strain-rate dependence of anelasticity on proof stress measurement of Mg alloys are also discussed.