Loading dependence and tension–compression asymmetry of deformation twinning in textured Mg-3Al-1Zn alloy: A multiscale synchrotron X-ray study

We investigate deformation dynamics in a textured magnesium alloy under uniaxial tension and compression along two different directions. The loading axis (LA) is either parallel or perpendicular to the normal direction (ND), referred to as LA$\parallel$ND tension/compression and LA$\perp$ND tension/compression, respectively. Stress$-$strain curves are measured simultaneously with X-ray diffraction and strain field mapping via synchrotron X-ray digital image correlation. Massive $\left\{10\bar{1}2\right\}$ extension twins are observed in the LA$\parallel$ND tension and LA$\perp$ND compression specimens. The growth rate of tension-induced twins is lower than that of compression-induced twins, likely because the pyramidal $〈c+a〉$ slips accommodate partial deformation along the $c$-axis in the LA$\parallel$ND tension specimen. Both the tension- and compression-induced deformation twins can slow down the process of strain localization, and thus an increase in strain hardening rate as well as the anisotropy in plastic deformation. The plastic strain ratios depend on strain localization and the relative orientation of the loading direction with respect to the basal texture, and are much larger in tension than in compression.