Inducement of kink-band formation in directionally solidified Mg/Mg17Al12 eutectic alloy - Inspired by the deformation behavior of the long-period stacking ordered (LPSO) phase

Abstract

Kink-band formation has received significant attention, especially in the Mg-based long-period stacking ordered (LPSO) phase which increases the strength and ductility of Mg alloys. However, its formation criteria are not understood. Recent studies suggested that unique LPSO crystal structure, which is constructed by alternative stacking of soft and hard layers, is a plausible factor governing the kink-band formation. To confirm this assumption, we examined the deformation behavior of a directionally solidified Mg/Mg17Al12 eutectic alloy with lamellar microstructure as a model material.Consequently, kink-band formation was indeed confirmed when stress was applied parallel to the lamellar interface. Interestingly, the hard Mg17Al12 phase rather than the soft Mg phase was found to predominately govern the kink-band formation behavior, contrary to the expectation. This must be because the easiest slip plane in Mg17Al12 is nearly parallel to the lamellar interface, which is not the case in Mg. The obtained results show that restricting the shear deformation direction in the material is the most important factor to induce kink-band formation. Furthermore, the distribution of a kink band could be controlled by introducing primary Mg17Al12 grains. The results provide new insight into a strategy for the aggressive use of kink band to improve the mechanical properties of structural materials.