Kink strengthening mechanism due to multiple kink bands in long-period stacking ordered magnesium alloy

In this study, we numerically investigate the strengthening mechanism in long-period stacking ordered magnesium alloys with two or more kink bands using a higher-order gradient crystal plasticity. From the viewpoint of crystalline-scale mechanics, kink strengthening in specimens with multiple kink bands can be attributed to three primary mechanisms, namely, orientation, defect, and neighboring strengthening. Among these, neighboring strengthening is a novel strengthening mechanism discovered in this study. As the spacing between kink bands decreases, the amplitude of kink strengthening increases. The sum of kink angles is more strongly correlated with the amplitude of kink strengthening than the number of kink boundaries and exhibits an obvious positive relationship with flow stress. The size effect on kink strengthening is also investigated. It is found that kink strengthening exhibits Hall–Petch-like behavior, exhibiting a linear correlation between the inverse of the square root of the kink band width and flow stress. Neighboring strengthening enhances the size effect as the spacing between kinks decreases. • Kink strengthening mechanism in LPSO-type magnesium alloy is numerically investigated. • A narrowing kink band spacing triggers a novel strengthening mechanism. • The presence of multiple kink bands enhances kink strengthening. • The sum of kink angles is a suitable indicator for evaluating the amplitude of kink strengthening. • The size effect of kink strengthening can be expressed using the Hall–Petch like relation.