Investigation on Slip Activity and Plastic Heterogeneity of Aged Mg–10Y Sheets During Compression

Abstract

Detailed quasi-in-situ grain-by-grain slip trace analysis and EBSD analysis were performed on the as-extruded, under-aged, and peak-aged Mg–10Y (wt pct) sheets to investigate the precipitate effects on the individual slip activities and plastic heterogeneity during room temperature compression. The sheet exhibited a significant age-hardening response whose yield strength increased by 63 pct after the peak-aged treatment. In the as-extruded condition, deformation was dominated by pyramidal II $\langle c + a\rangle$ slip (42.3 pct) followed by basal $\langle a\rangle$ slip (31.0 pct) and then pyramidal I $\langle c + a\rangle$ slip (21.1 pct). After the peak-aged treatment, the frequency of basal $\langle a\rangle$ slip increased to ~ 70 pct, and the pyramidal I/II slips significantly decreased to ~ 20 pct, which indicates the precipitate strengthening on pyramidal $\langle c + a\rangle$ slips was significantly over basal $\langle a\rangle$ slip. Most activated slip systems (68.2 pct) exhibited large normalized Schmid factors (${m}_{\mathrm{nor}}$> 0.3), but substantial (18.2 pct) hard-oriented slip systems (${m}_{\mathrm{nor}}$< 0.1) were also activated, suggesting local stress deviation. The magnitude/distribution of intragranular misorientation angle and geometrically necessary dislocation (GND) density inside a grain cannot be correlated with the visibility of slip trace from a statistical viewpoint. The extremely high GND density near grain boundary (GB) was closely related to (i) significant disparity of max Schmid factors for a particular slip mode and/or (ii) high GB misorientation between adjacent grains.