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 dislocations, while the LAKB in Mg interlayers sandwiched between LPSO phases is composed of an array of dissociated and/or 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 0.1-1.6 mJ m−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.