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

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. I-2 stacking fault (SF) is meanwhile generated in Mg layers, and its energy is evaluated approximately 0.1-1.6 mJ m(-2). Deformation-induced LAKBs, the resultant redistribution of solute elements, and precipitated I-2 SFs, are proposed to be responsible for the high strength of extruded Mg alloys containing LPSO structures.