Multiaxial behaviour of wrought magnesium alloys - A review and suitability of energy-based fatigue life model

Different wrought magnesium alloys from AM, AZ, and ZK family in the form of extrusion, rolled sheet and rolled plate have been selected for this study. Monotonic and cyclic behaviours are presented and compared. In particular, multi axial behaviours under proportional and non-proportional loadings are discussed. Despite the differences between the investigated alloys, it has been found that these alloys exhibit similar monotonic and cyclic characteristics. The similarity is attributed to the limited slip system in HCP magnesium, and the dominant role of deformation twinning in causing yield and hardening asymmetry. With strain energy density merit as a suitable fatigue parameter, it is therefore hypothesized that a simple two-parameter energy-based fatigue model is capable of correlating fatigue life of wrought magnesium alloys irrespective of material process, loading conditions and loading orientations. The hypothesis is then tested over a large number of fatigue results (354 tests). It is shown that fatigue lives predicted using the energy-life model are in good agreement with experimental results. Such simple model may prove to be useful in the early design stages lightweight components out of magnesium alloys.