It is well-established that Mg-3Al-1Zn (AZ31) alloy exhibits much better tensile ductility than pure Mg. However, the underlying mechanisms for such difference still remain relatively unexplored at the dislocation level. In this work, we deformed hot-rolled highly-textured pure Mg and AZ31 samples with similar initial microstructures (i.e., grain size and texture) under tension along the rolling direction. Apparent shear banding was only observed in the pure Mg samples from the early stage of the deformation. Shear bands could act as easy paths for crack propagation, leading to low ductility in pure Mg. Apparent shear banding was not noted in deformed AZ31 samples. We then investigated the deformation mechanisms at the dislocation level using transmission electron microscopy. Systematic tilting experiments and statistical analyses of multiple grains at different strain levels revealed a significant disparity of non-basal dislocation activities between pure Mg and AZ31. For pure Mg, <c + a> dislocations were activated since the early stage of plastic deformation. For AZ31, <c + a> dislocations were mostly absent at all strain levels, even in the strain-to-failure samples. Non-basal <a> dislocations, including prismatic and pyramidal <a> dislocations, were observed. The promotion of the non-basal <a> dislocation activities and the suppression of <c + a> dislocations in AZ31 are expected to offer more sustainable hardening, which could elucidate the absence of apparent shear banding and much-improved ductility in AZ31 compared to pure Mg.

公认的是，Mg-3Al-1Zn（AZ31）合金比纯Mg表现出更好的拉伸延展性。但是，在位错水平上，仍未充分探讨造成这种差异的潜在机制。在这项工作中，我们在沿轧制方向施加张力的情况下，对具有类似初始微观结构（即晶粒大小和织构）的热轧高织构高纯Mg和AZ31样品进行了变形。从变形的早期开始，仅在纯Mg样品中观察到表观剪切带。剪切带可以作为裂纹扩展的简单路径，从而导致纯镁的延展性降低。在变形的AZ31样品中未发现明显的剪切带。然后，我们使用透射电子显微镜在位错水平上研究了变形机理。系统的倾斜实验和不同应变水平下多个晶粒的统计分析表明，纯Mg和AZ31之间的非基极位错活动存在显着差异。对于纯镁，从塑性变形的早期开始，<c + a>位错被激活。对于AZ31，即使在应变失效样品中，在所有应变水平下也几乎没有<c + a>位错。观察到非基底性<a>位错，包括棱柱形和金字塔形<a>位错。促进AZ31中非基础<a>位错活动的促进和<c + a>位错的抑制将提供更可持续的硬化，这可以说明与纯镁