Deformation mechanisms of as-extruded Mg–3Bi–1Ca (wt.%) alloy during room-temperature tension

In this work, the deformation mechanisms of the as-extruded Mg–3Bi–1Ca (BX31, wt.%) alloy with strength-ductility synergy during room-temperature tension were studied in detail by in-situ electron backscattered diffraction (EBSD), slip trace analysis, visco-plastic self-consistent (VPSC) modeling and transmission electron microscopy (TEM). The quantitative results of in-situ EBSD and slip trace analysis showed that basal slips offered most of the deformation at the early stage, and with increasing strains the proportions of non-basal slips and {10-12} extension twinning gradually increased. At the medium and later stages, each deformation mode approached to be stable and the macroscopic strain became uniform. The critical resolved shear stresses (CRSSs) of different dislocation slip systems were estimated to establish the VPSC modeling. The VPSC-simulated results were highly consistent with the experimental ones. On the other hand, the microcosmic deformation incompatibility gave rise to the hetero-deformation induced (HDI) stress, caused by the distinct schmid factor (SF) and the low geometrical compatibility factor (m’) between adjacent grains. Geometrically necessary dislocations (GNDs, especially for the pyramidal edge dislocations) near grain boundaries would be generated to accommodate the deformation incompatibility. In addition, the basal screw dislocations in {10-12} extension twin interiors were also observed, which provided the extra strain hardening capacity.