Tension-compression asymmetry and the underlying slip/twinning activity in extruded Mg - Y sheets

The asymmetric mechanical response and corresponding statistical grain-scale slip/twinning activity for extruded Mg-(0 similar to 5 wt%)Y sheets during room-temperature uniaxial tension and compression along the extruded direction were investigated using slip trace analysis and EBSD-based misorientation analysis. The tension-compression asymmetry, in terms of yield strength, ultimate strength and uniform elongation, reduced with the addition of 0.5% Y to Mg. Increasing the Y concentration to 5% resulted in a reversed yield asymmetry (compressive yield strength > tensile yield strength). The non-basal slip activity increased (up to 31%) and the twinning activity decreased with increasing Y content, for both tension and compression. The Y-induced texture change did not significantly affect the pyramidal slip, while it promoted basal slip and suppressed prismatic slip. The observed trends of the slip activity suggested that the critical resolved shear stress (CRSS) ratios of CRSSpyramidal /CRSSbasal and CRSSpyramidal /CRSSprismatic decreased with Y addition. The correlation between macroscopic asymmetric behavior and slip/twinning activity implied that the pronounced pyramidal slip, together with the negligible twinning, were responsible for the reversed yield asymmetry. A higher activity of pyramidal slip was observed when the slip plane underwent tension compared with that for compression.

Automated summary

The addition of different concentrations of Y significantly affected the mechanical properties, grain-scale slip activity, and orientation heterogeneity of extruded Mg alloys during tension and compression. Increasing Y content led to noticeable changes in slip activity, while tension-compression asymmetry also showed variations.