Dislocation configuration and solute redistribution of low angle kink boundaries in an extruded Mg–Zn–Y–Zr alloy

Abstract

The microstructural and chemical features of deformation-induced interfaces are one of key issues in engineering materials because they determine plastic deformation behavior and thus affect mechanical properties of the materials. Using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy, we characterized deformation-induced low angle kink boundaries (LAKBs) in long period stacking ordered (LPSO) structures in an extruded Mg–2.3Zn–6.6Y–0.56Zr (wt%) alloy. We clarified that the LAKB in LPSO phase consists of an array of <a> dislocations, while the LAKB in Mg interlayers sandwiched between LPSO phases is composed of an array of dissociated <c+a> and/or <a> dislocations. Correspondingly, the former and the latter LAKBs are depleted and segregated with Zn/Y/Zr elements, respectively. I2 stacking fault (SF) is meanwhile generated in Mg layers, and its energy is evaluated approximately 0.1–1.6mJm−2. Deformation-induced LAKBs, the resultant redistribution of solute elements, and precipitated I2 SFs, are proposed to be responsible for the high strength of extruded Mg alloys containing LPSO structures.