The onset of twinning in metals:: A constitutive description
The onset of twinning in metals:: A constitutive description
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DOI：
10.1016/s1359-6454(01)00300-7
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发表时间：
2001-11-14
期刊：
影响因子：
9.4
通讯作者：
Lubarda, VA
中科院分区：
文献类型：
--
作者：
Meyers, MA;Vöhringer, O;Lubarda, VA
本构的方法，预测作为外部（温度，应变速率）和内部（晶粒尺寸，层错能）参数的函数的孪生临界应力。塑性变形的滑移和孪生被认为是竞争机制。孪晶应力等同于滑移应力的基础上的塑性流动的热辅助运动的位错在障碍物，这导致了成功的预测的滑移孪晶转变。该模型适用于体心立方，面心立方，六方金属和合金：铁，铜，黄铜，钛，分别。利用位错源的发射和堆积的形成作为速率控制机制，提出了体心立方金属中孪晶应力的本构表达式。采用Eshelby型分析，孪晶核的临界尺寸和孪晶应力与孪晶界面能相关，孪晶界面能与FCC金属的层错能（SFE）直接相关。晶粒尺寸和超临界流体的影响进行了检查，结果表明，晶粒尺度堆积的应力集中引起的FCC金属中的孪生的来源。滑移孪晶过渡的本构描述被纳入韦特曼-阿什比变形机制图，从而使引入的孪晶域。这对于晶粒尺寸为100 μ m的钛进行了说明。(C)2001 Acta Materialia Inc，由Elsevier Science Ltd.出版。保留所有权利。
A constitutive approach is developed that predicts the critical stress for twinning as a function of external (temperature, strain rate) and internal (grain size, stacking-fault energy) parameters. Plastic deformation by slip and twinning are considered as competitive mechanisms. The twinning stress is equated to the slip stress based on the plastic flow by thermally assisted movement of dislocations over obstacles, which leads to successful prediction of the slip-twinning transition. The model is applied to body centered cubic, face centered cubic, and hexagonal metals and alloys: Fe, Cu, brasses, and Ti, respectively. A constitutive expression for the twinning stress in BCC metals is developed using dislocation emission from a source and the formation of pile-ups, as rate-controlling mechanism. Employing an Eshelby-type analysis, the critical size of twin nucleus and twinning stress are correlated to the twin-boundary energy, which is directly related to the stacking-fault energy (SFE) for FCC metals. The effects of grain size and SFE are examined and the results indicate that the grain-scale pile-ups are not the source of the stress concentrations giving rise to twinning in FCC metals. The constitutive description of the slip-twinning transition are incorporated into the Weertman-Ashby deformation mechanism maps, thereby enabling the introduction of a twinning domain. This is illustrated for titanium with a grain size of 100 mum. (C) 2001 Acta Materialia Inc, Published by Elsevier Science Ltd. All rights reserved.