A continuum thermodynamic framework for grain boundary motion
A continuum thermodynamic framework for grain boundary motion
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DOI：
10.1016/j.jmps.2019.103827
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发表时间：
2020-04
影响因子：
5.3
通讯作者：
I. Chesser;Tingting Yu;C. Deng;E. Holm;B. Runnels
中科院分区：
文献类型：
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作者：
I. Chesser;Tingting Yu;C. Deng;E. Holm;B. Runnels
在这项工作中，我们试图解释晶界运动作为一个耗散过程中的热力学框架内的连续模型的晶体塑性。这使得一个统一的解释现象，如运动的驱动力，剪切耦合，模式切换，停滞。我们开始与晶界运动的运动学要求和晶界剪切变换的兼容性的讨论。该模型基于最小耗散势原理，其中“双耗散势”是由于界面运动而导致的单位转换体积的能量损失。几个分析实例表明，该模型一致地恢复多种类型的晶界迁移行为，表明耗散电位是一种固有的晶界属性。它还表明，该模型预测的模式切换的现象，并可以构建一个“屈服面”的机械加载模式选择和产量。然后使用分子动力学来测量大量边界的耗散势值（特别是“耗散能”）。速率无关的耗散能确定为一组晶体学不同的112镍晶界使用原子模拟与两种不同类型的物理驱动力：施加的应力和能量跳跃。跨驱动力的耗散能的协议提供了验证的框架。该模型的迁移机制的简化提供了一个基础，统一观察到的不同的晶界迁移行为的晶体学，驱动力和边界条件。最终，这个框架可以用来开发实验校准模型的晶界迁移在中尺度。
In this work, we seek to explain grain boundary motion as a dissipative process within a thermodynamic framework inspired by continuum models for crystal plasticity. This allows for a unified explanation of phenomena such as motion by driving force, shear coupling, mode switching, and stagnation. We begin with a discussion of the kinematic requirements for grain boundary motion and the compatibility of grain boundary shear transformations. The model is based on the principal of minimum dissipation potential, where the “dual dissipation potential” is the energy loss per unit transformed volume as a result of interface motion. Several analytical examples are shown to demonstrate that this model consistently recovers multiple types of grain boundary migration behavior, indicating that the dissipation potential is an intrinsic grain boundary property. It is also shown that the model predicts the phenomenon of mode-switching, and that a “yield surface” can be constructed to relate mechanical loading to mode selection and yield. Molecular dynamics is then used to measure dissipation potential values (in particular the “dissipation energy”) for a wide number of boundaries. Rate-independent dissipation energies are determined for a crystallographically diverse set of 112 Ni grain boundaries using atomistic simulations with two distinct types of physical driving forces: an applied stress and energy jump. Agreement of dissipation energies across driving forces provides verification for the framework. The model’s simplification of migration mechanisms provides a basis for unifying the observed varied grain boundary migration behavior subject to crystallography, driving force, and boundary conditions. Eventually, this framework can be used to develop experimentally calibrated models of grain boundary migration at the mesoscale.