Effect of redundant shear strain on microstructure and texture evolution during accumulative roll-bonding in ultralow carbon IF steel
Effect of redundant shear strain on microstructure and texture evolution during accumulative roll-bonding in ultralow carbon IF steel
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DOI：
10.1016/j.actamat.2007.07.002
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发表时间：
2007-10-01
期刊：
影响因子：
9.4
通讯作者：
Tsuji, N.
中科院分区：
文献类型：
--
作者：
Kamikawa, N.;Sakai, T.;Tsuji, N.
累积叠轧焊（ARB）是一种强塑性变形工艺，可以有效地在金属和合金中产生超细晶（UFG）组织。在以前的研究中，ARB过程经常在材料和辊之间没有任何润滑剂的高摩擦条件下进行，这可能会导致板表面附近的大量冗余剪切应变。由于在ARB中重复切割、堆叠和辊压，预计通过板厚度的复杂冗余剪切应变分布。本研究的目的是阐明多余的剪切应变对ARB过程中的组织和织构演变的影响。添加Ti的超低碳无间隙原子钢在500 ℃下通过多达7个循环的ARB（厚度减少99.2%）变形，有或没有润滑，以研究剪切应变的影响。通过电子背散射衍射分析在ARB处理的片材的不同厚度位置处进行微观结构表征。在良好润滑条件下，经过一个循环的ARB处理后的板材在整个厚度范围内呈现出均匀的典型变形组织。与此相反，一个ARB循环没有润滑处理的试样有一个不均匀的显微组织，和变形引起的高角度边界的分数增加接近表面。非润滑ARB在低循环次数下引起全厚度显微结构不均匀性，但重复ARB超过5个循环最终产生相当均匀的UFG结构。结果表明，变形结构的微观结构参数基本上可以用总等效应变来理解，并考虑了多余的剪应变。(C)2007 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Accumulative roll-bonding (ARB) is a severe plastic deformation process that can effectively produce ultrafine grained (UFG) structures in metals and alloys. In previous investigations, the ARB process has often been carried out under high-friction conditions without any lubricant between materials and rolls, which may cause a large amount of redundant shear strain near the sheet surface. Owing to repetition of cutting, stacking and roll-bonding in the ARB, a complicated redundant shear strain distribution is expected through the sheet thickness. The purpose of the present study is to clarify the effect of the redundant shear strain on the microstructure and texture evolution during ARB. A Ti-added ultralow carbon interstitial free steel was deformed by up to seven cycles of ARB (a thickness reduction of 99.2%) at 500 degrees C, with or without lubrication, in order to investigate the effect of shear strain. Microstructural characterization by electron backscatter diffraction analysis was carried out at various thickness locations of the ARB processed sheets. The sheet processed by one cycle of ARB with good lubrication showed typical deformation microstructures uniformly throughout the thickness. In contrast, the specimen processed by one ARB cycle without lubrication had an inhomogeneous microstructure, and the fraction of deformation-induced high-angle boundaries increased close to the surface. Non-lubricated ARB caused through -thickness microstructural heterogeneity in low numbers of cycles, but repetition of ARB above five cycles finally produced quite uniform UFG structures. It was established that the microstructural parameters of the deformation structures can be basically understood in terms of the total equivalent strain, taking account of the redundant shear strain. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.