The deformation behaviors of a hot-extruded Mg-2wt%Y alloy sheet with high activity for basal slip was studied under uniaxial tensile loading along the extrusion direction at room temperature. Using electron backscatter diffraction and crystal plasticity finite element method (CPFEM) simulation, this work proposed the direct evidence for the activation and the role of anomalous {$10\bar{1}2$} twinning: (1) In the Mg alloy with high activity for basal slip, anomalous {$10\bar{1}2$} twins were indeed identified during tensile loading rather than unloading. The anomalous twins had the highest or the third highest negative Schmid factors of {$10\bar{1}2$} twinning, while the normal twins had positive Schmid factors. (2) During tensile loading, the anomalous twins were more easily activated than normal twins. As the true strain increased, the amounts of anomalous twins increased faster than the amounts of normal twins. (3) The normal twins induced positive shear strain along the loading direction while the anomalous twins induced negative shear strain along the loading direction. The role of anomalous twinning was accommodating the plastic compatibility and improving the ductility.

研究了在室温下沿挤压方向在单轴拉伸载荷下对基体滑移具有高活性的Mg-2wt％Y合金热挤压板的变形行为。使用电子背散射衍射和晶体可塑性有限元方法（CPFEM）模拟，这项工作为异常的激活和作用提供了直接证据{$10\stackrel{〜}{\mathrm{1个}}2$}孪晶：（1）在对基层滑移具有高活性的Mg合金中，反常{$10\stackrel{〜}{\mathrm{1个}}2$}确实在拉伸载荷而不是卸载过程中发现了孪晶。异常双胞胎的负Schmid因子为{$10\stackrel{〜}{\mathrm{1个}}2$孪生，而正常双胞胎的Schmid因子为正。（2）在拉伸载荷下，异常双胞胎比正常双胞胎更容易被激活。随着真实应变的增加，异常双胞胎的数量增长快于正常双胞胎的数量。（3）正常双胞胎沿载荷方向产生正剪应变，反常双胞胎沿载荷方向产生负剪应变。异常孪生的作用是适应塑料的相容性并改善延展性。