Understanding the enhanced ductility of Mg-Gd with Ca and Zn microalloying by slip trace analysis

This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis. The ductility and microstructure of extruded Mg-0.6Gd and Mg-0.6Gd-0.3Ca-0.2Zn(wt%) sheets were investigated.Basal slip was the main deformation mode under investigation. Ca and Zn microalloying increased the frequency of grain boundaries(GBs) with misorientation angles(θ s) < 35°, promoted slip transfer across GBs and restricted the basal slip localization. In addition, there were a higher number of GB cracks homogeneously distributed in the Mg-0.6Gd sheet than in the Mg-0.6Gd-0.3Ca-0.2Zn sheet, attributed to the increased cohesion of GBs. The enhancement of basal slip, the suppression of slip localization and the suppression of GB cracking were contributed to the increased ductility for Mg-0.6Gd-0.3Ca-0.2Zn sheet.