Quantitative study on slip/twinning activity and theoretical critical shear strength of Mg alloy with Y addition.

Slip/twinning activity and theoretical critical shear strengths (τ max) during room-temperature tensile deformation of as-extruded pure Mg and Mg-1wt.%Y sheets were investigated quantitatively via electron back-scattered diffraction (EBSD), scanning electron microscope (SEM) and first-principles calculation. Slip trace analysis results indicated the relative frequency of the active slip modes transformed from basal slip (100%) for pure Mg, to basal slip (84.8%), prismatic slip (9.7%) and pyramidal slip (5.5%) for the alloy. The proportion of grains containing twins reduced significantly from 20.5% to 5.92% with Y addition. To explain the mechanism for the enhancement of the non-basal slip activity in Mg–Y alloy, the critical resolved shear stress of basal slip and pyramidal II slip were assessed by calculating τ max. The calculated results showed that the τ max ratio of the pyramidal II slip to basal slip decreased from 13.7 to 7.5, which may be responsible for the observed enhanced activity of non-basal slip. [ABSTRACT FROM AUTHOR]