Study of Grain Boundary and Dislocation Transmission based on a Finite-Deformation Framework with an Application to Description of Nanoindentation Tests

基于有限变形框架的晶界和位错传递研究及其在纳米压痕测试描述中的应用

• 批准号: 437367132
• 负责人: Professor Dr.-Ing. Karsten Durst
• 金额: --
• 依托单位: Fachgebiet Physikalische Metallkunde
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437367132?language=en
• 关键词: Study; Grain; Boundary; Dislocation; Transmission

Grain boundaries (GBs) play an important role in the plastic deformation of metals carried out by the motion of dislocations. Indentation tests close to grain boundaries have also shown the occurrence of dislocation pile-up and then transmission of dislocations through GBs in a so called GB pop-in event. This proposal will address the complexity of interactions between dislocations and grain boundaries as well as the effect of grain boundaries on the dislocation motions based on a finite-deformation gradient crystal-plasticity framework. The thermodynamically consistent model includes the energetic and dissipative governing components and is first accompanied with a yield function controlling microtractions associated with the densities of dislocations accumulated at grain boundaries and then extended to incorporate automatically the effect of the relative misorientation of adjacent grains at the grain boundary. The model is developed based on a novel approach and implemented in the finite-element software ABAQUS. The numerical work is supported by nanoindentation and high resolution electron microscopy on reference bcc materials. The grain boundary pop-in behavior is studied for different grain boundary misorientations using nanoindentations with Berkovich and spherical indenters. The nanoindentation experiments will compromise a wide range of rate and size dependent studies, quantifying the GB pop-in effect in dependence of the indentation distance to GBs and the indenter orientation. Furthermore, sequential polishing and high resolution electron back scatter diffraction (HR-EBSD) is used to assess the local orientation gradients around the residual impressions for indentations within grain interior as well as indentations exhibiting the GB pop-in. This research work will provide a comprehensive description of the dislocation grain boundary interaction, based on a combined theoretical and experimental approach.

晶界在金属的塑性变形过程中起着重要的作用。在晶界附近的压痕试验也显示了位错堆积的发生，然后在所谓的GB弹出事件中位错通过GB的传输。这一建议将解决位错和晶界之间的相互作用的复杂性，以及晶界上的位错运动的有限变形梯度晶体塑性框架的基础上的效果。该模型包括能量和耗散的控制组件，并首先伴随着屈服函数控制微牵引与位错的密度在晶界处积累，然后扩展到自动纳入相邻晶粒的相对取向差的影响在晶界处。该模型是基于一种新的方法开发的，并在有限元软件ABAQUS中实现。数值计算工作的支持下，纳米压痕和高分辨率电子显微镜的参考体心立方材料。采用布氏压痕和球形压痕对不同晶界取向差下的晶界弹入行为进行了研究。纳米压痕实验将妥协广泛的速率和尺寸相关的研究，量化的GB弹出效果的压痕距离，以GB和压头方向的依赖。此外，顺序抛光和高分辨率电子背散射衍射（HR-EBSD）是用来评估周围的局部取向梯度的残余压痕内的晶粒内部以及压痕表现出GB弹出。这项研究工作将提供一个全面的描述位错晶界相互作用的基础上相结合的理论和实验方法。