In-situ TEM characterization of basal dislocations between nano-spaced long-period stacking ordered phases in MgYZn alloy

Abstract

Long-period stacking ordered (LPSO) phases play strong barriers to the motion of non-basal dislocations and deformation twins, effectively improving the strength of Mg alloys. Corresponding to the crystallographic character of LPSO phases, it is generally believed that LPSO phases would not affect the motion of basal dislocations. Here, we perform in-situ TEM nanoindentation testing in a single crystal specimen of Mg97Y2Zn alloy that contains LPSO phases with various spacing within 100 nm, and report on a significantly low activity of basal dislocations in Mg matrix between LPSO phases with spacing less than 20 nm. Atomic HADDF-STEM results reveal a high concentration of solute atoms near LPSO phases, which could provide strong solute strengthening effect. These findings may provide possible guidance to design ultra-high strength of Mg alloys containing nano-spaced LPSO phases.