Effects of LPSO/α-Mg interfaces on dynamic recrystallization behavior of Mg96.5Gd2.5Zn1 alloy

Mg-Gd-Zn alloy, which contains a long period stacking ordered (LPSO) structure, has the potential to become a high-strength Mg alloy within the automotive and aerospace industries. Two types of LPSO/alpha-Mg interfaces in Mg96.5Gd2.5Zn1 (at.%) alloy were characterized, namely, basal and non-basal LPSO/alpha-Mg interfaces. The effects of LPSO/alpha-Mg interfaces on the dynamic recrystallization (DRX) behavior during indirect extrusion at 350 degrees C were investigated. The grain reference orientation deviation (GROD) value (V-GROD), derived from EBSD, could qualitatively characterize the dislocation density within a grain and determine the presence of DRX grain nucleation. The results suggested that the areas around non-basal LPSO/alpha-Mg interfaces always have higher V-GROD than do basal LPSO/alpha-Mg interfaces. In addition, the stored energy (E-s) required for DRX nucleation on the non basal LPSO/alpha-Mg interface is lower than that on the basal LPSO/alpha-Mg interface. This is a result of the flat, sharp basal LPSO/alpha-Mg interface compared to the faceted non-basal LPSO/alpha-Mg interface. Regardless of whether the LPSO structure/alpha-Mg matrix interface is coherent or not, non-basal LPSO/alpha-Mg interfaces are favorable nucleation sites for DRX grains due to the higher VGROD and lower required energy E-s.