In-situ analysis of the tensile deformation modes and anisotropy of extruded Mg-10Gd-3Y-0.5Zr (wt.%) at elevated temperatures

Abstract

The deformation modes and anisotropic behavior during the tensile deformation of peak-aged extruded Mg-10Gd-3Y-0.5Zr (wt.%) at 200, 250 and 300 °C were investigated using in-situ scanning electron microscopy. The samples tested along the extrusion direction (ED) exhibited the highest strength and the samples tested perpendicular to the extrusion direction (TD) exhibited the lowest strength, while the samples oriented 45° to the ED exhibited intermediate strength. Dislocation slip was the main deformation mode during the tensile deformation, while grain boundary sliding contributed to the deformation at 300 °C. No twinning was observed. Non-basal slip accounted for 21%, 7% and 36% of the total active slip systems at 200 °C for the ED, TD and 45° samples, respectively. The non-basal slip contribution to the total active slip systems was 12–17% at 250 °C, and it decreased to 3–5% at 300 °C. Multiple-slip was observed and there were more multiple-slip observations at lower temperatures (200 and 250 °C) compared to those at 300 °C. Basal-prismatic pairing type predominated the multiple-slip observations and the involved slip systems were associated with different <a> slip directions. Slip transfer across grain boundaries occurred at 200 and 250 °C. The slip systems of the observed slip transfer pairs were always associated with the same <a>. Slip transfer occurred more easily at low angle grain boundaries (LABs) and grain boundaries with angles higher than 75°. Intergranular cracking was the main cracking mode. Cracks were more likely to initiate at the grain boundaries where the neighboring grains were in hard orientations for basal slip.