Dislocation-induced plastic instability in a rare earth containing magnesium alloy

Abstract

An uncommon yield point phenomenon is observed in a Mg-1.5 wt.%Nd extrusion alloy deformed in tension. The stress-strain curve exhibits a drop at the onset of yielding, which is followed by a prolonged plateau stage prior to normal strain hardening. Localized deformation bands are observed to nucleate at the upper yield stress and propagate during the yield plateau. The yield plateau exists independent of texture and grain size of the material and shows a small dependence on strain rate. It is hypnotized that the yield point phenomenon is caused by the interactions between mobile dislocations and solute clusters. Specifically, the localized deformation at the front of deformation bands is a consequence of glide carried out by dislocations being unlocked from solute clusters by stress-strain fields from propagating bands, while dislocations away from the bands remain locked and material swept by the bands hardens.