Anomalous strain hardening via manipulating basal/pyramidal dislocation interactions in the Mg-Y-Ca alloy

Easy activation of basal <a> dislocation causes limited ductility of magnesium, which exhibits insufficient strain hardening, leading to the localization of plastic deformation, instability and crack nucleation. Here, micropillar compression tests in a magnesium-yttrium-calcium alloy found an anomalous strain hardening phenomenon induced by interactions between basal <a> and pyramidal <c+a> dislocations. Dislocation interactions generate strong obstacles that inhibit the continuous slip of basal <a> dislocations, preventing deformation instabilities associated with basal slip localization. Meanwhile, the strain hardening is enhanced during plastic deformation, which would otherwise be limited by the easy glide of basal <a> dislocations. Additionally, the activation of more <c+a> dislocations contributes to improved ductility. These dislocation interactions can be tuned by activating multiple slips via reducing the critical resolved shear stress ratio between non-basal and basal slip systems. Overall, this study offers a new fundamental perspective on promoting strain hardening and overcoming strength-ductility trade-off in magnesium alloys.