Characterization of deformation microstructure of Mg alloys containing LPSO structure via transmission electron microscopy

形变孪晶内部的析出物会阻碍位错的运动，从而影响材料的力学性能。在此，在原子水平上，我们直接观察到含有长周期堆积有序(LPSO)结构的Mg-Zn-Y合金中的基位错滑移剪切了形变孪晶内的孪生层错(TSF)。富含溶质原子的TSFs可认为是形变孪晶中的析出物。它们在基面上通过单步或多步剪切来剪切。微观结构指纹，即基面剪切台阶的宽度，使得能够定量地评估由于变形孪晶内的基面位错所引起的局部和整体塑性剪切应变。TSFs能阻挡位错滑移，位错剪切引起较大的晶格变形，甚至在局部交点处溶质原子重新分布。TSFs-位错相互作用有望降低基础位错运动，从而调节镁合金的力学性能。这些结果可能为通过剪裁可剪切析出物来强韧化镁合金提供新的策略。

The precipitates inside deformation twins may block the dislocation motion and consequently affect the mechanical property of materials. Herein, at the atomic level, we directly visualize that the basal dislocation slips shear the twinned stacking faults (TSFs) within the deformation twins in an Mg-Zn-Y alloy containing long-period stacking ordered (LPSO) structures. The TSFs, enriched with solute atoms, could be considered as precipitates inside deformation twins. They are sheared by a single step or multiple shearing steps on the basal plane. The microstructural fingerprints, i.e., the width of basal shearing steps, enable a quantitative assessment of the local and total plastic shear strain due to the basal dislocation within the deformation twins. The TSFs can block dislocation slip, while the dislocation shearing induces large lattice distortion and even solute atoms redistribution at local intersection. The TSFs-dislocation interaction is expected to lower the basal dislocation motion and resultantly modulate the mechanical properties of magnesium alloys. These results may offer a novel strategy for strengthening and toughening magnesium alloys via tailoring the shearable precipitates.