Residual Ductility and Microstructural Evolution in Continuous-Bending-under-Tension of AA-6022-T4
Residual Ductility and Microstructural Evolution in Continuous-Bending-under-Tension of AA-6022-T4
复制标题
AA-6022-T4 连续拉伸弯曲中的残余延展性和微观结构演变
作者：
Milovan Zecevic;T. Roemer;M. Knezevic;Y. Korkolis;B. Kinsey
一个普遍存在的实验来表征金属板材的可成形性是简单的拉伸试验。过去的研究表明，如果材料在该测试期间反复弯曲和不弯曲（即，拉伸下连续弯曲（Continuous-Bending-under-Tension，CBT），断裂伸长率百分比可显著增加。在本文中，使用定制的CBT设备对AA-6022-T4片材的这种现象进行了详细评估。特别是，进行CBT处理的试样的剩余延性进行了研究。这是通过对试样进行CBT处理，然后在不同数量的CBT循环后从试样中创建子尺寸拉伸试验和微观结构样品来实现的。有趣的是，在CBT加工到一定数量的循环后，工程应力最初增加，但随后随着CBT循环数量的增加而实现的伸长率降低。此外，使用标准扫描电子显微镜和电子背散射衍射成像进行详细的微观结构和纹理表征。结果表明，CBT下的材料保持高的完整性，以大的塑性应变，由于均匀分布的损伤形成和演变的材料。在CBT过程中延迟韧性断裂到大塑性应变的能力导致<111>在整个材料中形成强纤维织构。
A ubiquitous experiment to characterize the formability of sheet metal is the simple tension test. Past research has shown that if the material is repeatedly bent and unbent during this test (i.e., Continuous-Bending-under-Tension, CBT), the percent elongation at failure can significantly increase. In this paper, this phenomenon is evaluated in detail for AA-6022-T4 sheets using a custom-built CBT device. In particular, the residual ductility of specimens that are subjected to CBT processing is investigated. This is achieved by subjecting a specimen to CBT processing and then creating subsize tensile test and microstructural samples from the specimens after varying numbers of CBT cycles. Interestingly, the engineering stress initially increases after CBT processing to a certain number of cycles, but then decreases with less elongation achieved for increasing numbers of CBT cycles. Additionally, a detailed microstructure and texture characterization are performed using standard scanning electron microscopy and electron backscattered diffraction imaging. The results show that the material under CBT preserves high integrity to large plastic strains due to a uniform distribution of damage formation and evolution in the material. The ability to delay ductile fracture during the CBT process to large plastic strains, results in formation of a strong <111> fiber texture throughout the material.