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工业纯铝在冷轧大变形过程中,屈服强度随应变量的增加先上升后降低。强度在等效应变为3.3时(εvM=3.3)达到峰值,之后随着压下量进一步增加,其强度反而下降,即出现了变形致软化的现象。透射电子显微镜观测两种样品(εvM=3.3和εvM=4.1)发现,造成这一现象的主要原因是材料内部微观结构不同。εvM=4.1的样品微观结构为冷轧大变形之后典型的层状结构;而εvM=3.3的样品中除含有典型层状结构之外,还包含近似等轴晶的区域,该区域中小角度晶界比例以及位错密度较高。通过理论计算位错强化与细晶强化的贡献,发现εvM=3.3的样品强度高于εvM=4.1的样品,与实验结果一致。
In the process of large cold deformation, the yield strength of industrial pure aluminum first increases and then decreases with the increase of strain. The strength peaked at an equivalent strain of 3.3 (εvM = 3.3), and then decreased as the reduction was further increased, thereby deforming softened. Transmission electron microscopy of the two samples (εvM = 3.3 and εvM = 4.1) found that the main reason for this phenomenon is the microstructure of the material is different. The sample microstructure with εvM = 4.1 is a typical lamellar structure after cold rolling and large deformation. However, the sample with εvM = 3.3 contains a typical lamellar structure with an approximately equiaxed zone in which small-angle grain boundaries The proportion and dislocation density are higher. By theoretical calculation of the contribution of dislocation enhancement and fine grain strengthening, it is found that the sample with εvM = 3.3 is higher than the sample with εvM = 4.1, which is consistent with the experimental results.