Strengthening of alloy AA6022-T4 by continuous bending under tension
Strengthening of alloy AA6022-T4 by continuous bending under tension
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DOI：
10.1016/j.msea.2019.04.109
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
M. Knezevic;C. Poulin;Xiaodong Zheng;Shijian Zheng;I. Beyerlein
中科院分区：
文献类型：
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作者：
M. Knezevic;C. Poulin;Xiaodong Zheng;Shijian Zheng;I. Beyerlein
本文研究了AA 6022-T4合金板材经连续弯曲-拉伸（CBT）预变形后的强度演变。只有在几个CBT周期后才能观察到强度的显著改善。随着CBT循环次数的增加，观察到强度的改善不太明显，并且随着每个循环，延展性降低。这些意见是合理化的微观结构的演变，利用透射电子显微镜和电子背散射衍射表征。结果表明，CBT过程中织构和晶粒形状的演变与单纯拉伸（ST）过程略有不同。此外，沉淀物不改变其形状在CBT或ST。因此，得出结论，这些微观结构特征只有一个次要的影响合金的强度行为。与文献中的早期观察相一致，我们发现，位错结构形成在晶粒内的单调ST，它们是无序的，并没有很好地定义。相比之下，观察到细胞亚结构在CBT处理过程中很早就形成了，甚至在第一个周期之后，并且在随后的周期中从松散的位错缠结演变为定义明确的壁。这些位错模式被发现负责所观察到的合金的行为。因此，材料的强度不仅取决于所获得的有效应变水平，还取决于所获得的微观结构。
This paper studies the evolution in strength of alloy AA6022-T4 sheets that have been pre-deformed by a continuous-bending-under-tension (CBT) process. Significant improvements in strength are observed only after a few CBT cycles. Less appreciable improvements in strength are observed with more CBT cycles and with every cycle the ductility reduces. These observations are rationalized by characterizing microstructural evolution using transmission electron microscopy and electron backscattered diffraction. It is found that evolution of texture and grain shape during CBT slightly differ from those in simple tension (ST). Also, the precipitates do not change their shape during CBT or ST. It is, therefore, concluded that these microstructural features have only a secondary effect on the strength behavior of the alloy. Consistent with earlier observations in the literature, we find that dislocation structures form within grains during monotonic ST and that they are disorganized and not as well defined. In contrast, cellular substructures are observed to form very early during CBT processing, even after the first cycle and to evolve from loose tangles of dislocations to well-defined walls during subsequent cycles. These dislocation patterns are found responsible for the observed behavior of the alloy. Therefore, the strength of the material is determined not only by the achieved effective strain level but also by achieved microstructure.