Grain size dependent texture evolution in severely rolled pure copper
Grain size dependent texture evolution in severely rolled pure copper
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DOI：
10.1016/j.matchar.2015.02.003
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发表时间：
2015-03
影响因子：
4.7
通讯作者：
C. Gu;M. Hoffman;L. Toth;Yudong Zhang
中科院分区：
文献类型：
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作者：
C. Gu;M. Hoffman;L. Toth;Yudong Zhang
对粗晶（CG，24 μm）和超细晶（UFG，360 nm）两种不同初始晶粒尺寸的纯铜进行了大变形轧制（厚度减薄率达97%）。轧制后，获得经典的铜型轧制织构的CG铜，而黄铜型轧制织构中观察到的起始UFG铜，获得八道次等通道角挤压在室温下轧制前。使用粘塑性自洽多晶体模型，它被发现，在大轧制应变的变形机制是晶粒尺寸依赖性和主要的滑移模式的变化有很大的影响的变形织构的类型。UFG材料中的黄铜型织构可以使用{111}< 11 2 <$$>>部分滑移以及{111}< 1 1 <$0>滑移和少量孪晶来模拟;对于CG材料，仅需要{111}< 1 1 <$0>滑移来再现铜型轧制织构。此外，它被发现，多晶变形条件接近泰勒行为在UFG材料，而更多的应变不均匀性存在于轧制的CG铜。通过取向成像电子显微镜的几何必要位错（GND）密度被发现是减少在UFG轧制样品，而增加在CG的情况下。这种趋势证实了纹理模拟参数应变异质性。
Large strain rolling–up to 97% thickness reduction–was carried out on pure copper with two different initial grain sizes: coarse-grained (CG, 24 μm) and ultrafine-grained (UFG, 360 nm). After rolling, classical copper-type rolling texture was obtained for the CG copper while a brass-type rolling texture was observed in the starting UFG copper, obtained by eight-pass equal channel angular pressing at room temperature prior to rolling. Using the Viscoplastic Self Consistent polycrystal model, it is found that the deformation mechanism at large rolling strain is grain size dependent and a change in the major slip mode has a large impact on the type of deformation texture. The brass-type texture in the UFG material can be simulated using {111}< 11 2¯> partial slip together with {111}< 1 1¯ 0> slip and a small amount of twinning; for the CG material, only {111}< 1 1¯ 0> slip is needed to reproduce the copper-type rolling texture. Further, it is found that the polycrystal deformation condition approaches Taylor behavior in the UFG material whereas much more strain heterogeneity is present in rolling of the CG copper. By orientation imaging electron microscopy the geometrically necessary dislocation (GND) density is found to be decreasing in the UFG rolled samples while increasing in the CG case. This tendency corroborates the texture simulation parameters concerning strain heterogeneity.