Macroscopic shear bands (MSB) may develop during hot working of metallic materials. They are well-understood as a physical manifestation of flow instability, and the processing regimes wherein they form are well-charted. However, the microstructural transitions that occur between the onset of flow instability and MSB inception are not fully understood. In order to elucidate them, several aluminum alloy specimens were subjected to strip testing in a thermomechanical simulator (Gleeble™) at 298 K and 573 K. Prominent MSB were observed along the diagonals of the strip volume of only Aluminum-6 wt% Magnesium alloy specimen deformed at 573 K. Comparing the experimental grain morphology and crystallographic textures with those from plastic flow models revealed that MSB inception occurred only after ∼0.20 homogeneous plane strain deformation. However, classical flow instability was predicted at much smaller strain. This ‘delay’ was explained experimentally by showing that clusters of neighbouring severely deforming, fragmenting, mostly soft-oriented grains gradually developed due to lattice rotations along the specimen diagonals, and that MSB inception corresponded to the formation of a percolating network of such grains spanning the specimen. Further, clear experimental evidence revealed that differential dynamic recovery between hard- and soft-oriented grains was essential for MSB formation.

在金属材料的热加工过程中可能会形成宏观剪切带 (MSB)。它们被很好地理解为流动不稳定性的物理表现，并且它们形成的处理机制被很好地绘制出来。然而，在流动不稳定开始和 MSB 开始之间发生的微观结构转变尚不完全清楚。为了阐明它们，几个铝合金样本在 298 K 和 573 K 的热机械模拟器 (Gleeble™) 中进行了条带测试。沿着只有铝-6 wt% 镁合金的条带体积的对角线观察到突出的 MSB样品在 573 K 时变形。将实验晶粒形态和晶体结构与塑性流动模型的晶粒形态和晶体结构进行比较，发现 MSB 仅在 ~0.20 均匀平面应变变形后发生。然而，在小得多的应变下预测了经典的流动不稳定性。这种“延迟”在实验上得到了解释，表明由于沿试样对角线的晶格旋转，相邻的严重变形、破碎、大部分为软取向的晶粒逐渐形成簇，并且 MSB 开始对应于此类晶粒跨越的渗透网络的形成标本。此外，明确的实验证据表明，硬取向和软取向晶粒之间的差异动态恢复对于 MSB 的形成至关重要。并且 MSB 的开始对应于跨越样本的此类颗粒的渗透网络的形成。此外，明确的实验证据表明，硬取向和软取向晶粒之间的差异动态恢复对于 MSB 的形成至关重要。并且 MSB 的开始对应于跨越样本的此类颗粒的渗透网络的形成。此外，明确的实验证据表明，硬取向和软取向晶粒之间的差异动态恢复对于 MSB 的形成至关重要。