Effect of the interspacing of intragranular lamellar LPSO phase on dynamic recrystallization behaviors of Mg-Gd-Y-Zn-Zr alloys

The microstructures with different interspacings of intragranular lamellar long period stacking ordered (LPSO) phase were designed by altering the cooling rate after solid solution heat treatment, and the effect of the interspacing on the dynamic recrystallization (DRX) of Mg-Gd-Y-Zn-Zr alloy was investigated. During hot compression in the temperature range of 350-500 degrees C and strain rate from 0.001 s-1 to 1 s-1, the water-quenched (WQ) alloy containing closely spaced LPSO lamellae exhibits higher peak stress, larger critical strain, and smaller area fraction of DRX grains than the furnace-cooled (FC) alloy containing widely spaced LPSO lamellae. It is concluded that closely spaced intragranular LPSO lamellae suppress DRX. We further revealed the underlying mechanism using EBSD analyses and TEM characterizations. The larger lamellar LPSO interspacing imposes a much weaker constraint on the activation of the non-basal [c]-containing dislocations, which act as obstacles for the gliding dislocations and hence offer favorable conditions for continuous DRX (CDRX). These findings provide a microstructural guidance for tuning the hot formability of LPSO-containing Mg alloys.

Automated summary

This study designed microstructures with different interspacings of intragranular lamellar long period stacking ordered (LPSO) phase by altering the cooling rate after solid solution heat treatment, and investigated the effect of the interspacing on the dynamic recrystallization (DRX) of Mg-Gd-Y-Zn-Zr alloy. It was found that closely spaced intragranular LPSO lamellae suppress DRX. The underlying mechanism was further revealed using EBSD analyses and TEM characterizations.