Kink boundaries and their role in dynamic recrystallisation of a Mg-Zn-Y alloy

An as-cast Mg₉₄Zn₂Y₄ alloy has been subjected to compression and equal channel angular pressing separately; the resultant microstructure was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD). The as-cast Mg₉₄Zn₂Y₄ alloy contains a long-period stacking ordered (LPSO) phase and a Mg₂₄Y₅ phase. After the compression, kink boundaries are observed in the LPSO phase and are composed of straight basal ⟨a⟩ dislocations. The dislocation arrangement in the kink boundaries of the LPSO/Mg mixture (alternate thin layers of LPSO and Mg) is similar to that in the LPSO phase. The rotation axes of the kink boundaries in LPSO/Mg are preferentially located in the (0001) plane, though [0001] rotation axis has occasionally been observed. Double kinking and non-basal slip have also been observed in the LPSO/Mg mixture. Dynamically recrystallised Mg grains are observed in the kink boundaries located within the LPSO/Mg mixture, preferentially in the kink boundaries with high misorientation angles. The kink boundary acts as the nucleation site for dynamic recrystallisation due to the high energy stored.