Temperature-dependent interplay of intra- and inter-granular deformation mechanisms in Mg-10Y: Statistical analysis from an HRDIC perspective

To uncover the anomalous temperature-dependent slip activity (decreased non-basal slip activity with increasing temperature) in polycrystalline Mg-10Y (wt.%) during compression, the deformation mode activity was quantitatively investigated using high-resolution digital image correlation (HRDIC) and electron backscattered diffraction (EBSD) data fusion. The deformed microstructural patch that was characterized contained ~300 grains and ~800 grain boundaries (GBs), and ~45 million measured strain data were acquired to statistically interrogate both intra- and inter-granular mechanisms. From a strain-partitioning perspective, the competition between slip bands (SBs) and grain mantles (GMs, the region near GBs) was quantified. At 25 °C, the SB deformation, in terms of mean effective shear strain ratio (SR), was ~2.5 times greater than that of the GM. As temperature increased (up to 300 °C), the SR discrepancy between SB and GM decreased significantly. The prevailing SB mode transitioned from multiple slip at 25-200 °C to single slip at 300 °C; basal slip was dominant at 25 °C and the percentage of non-basal slip increased from 22.4% at 25 °C to 41.5% at 200 °C and then it anomalously decreased to 10.6% at 300 °C. At 300 °C, the surface GB sliding (GBS) increased significantly compared to that at 25 °C, with mean value of GBS displacements increasing from 1.2±7.8 to 18.3±27.9 nm and the percentage of GBs in which notable displacements were observed increased from 4.2% to 53.9%. This work emphasizes the importance of simultaneously evaluating both intra- and inter-granular deformation mechanisms for polycrystalline microstructures.