Liu F X, Cocks A C F, Tarleton E
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK.
Proc Math Phys Eng Sci. 2021 Jun;477(2250):20210083. doi: 10.1098/rspa.2021.0083. Epub 2021 Jun 16.
Plastic deformation in crystalline materials occurs through dislocation slip and strengthening is achieved with obstacles that hinder the motion of dislocations. At relatively low temperatures, dislocations bypass the particles by Orowan looping, particle shearing, cross-slip or a combination of these mechanisms. At elevated temperatures, atomic diffusivity becomes appreciable, so that dislocations can bypass the particles by climb processes. Climb plays a crucial role in the long-term durability or creep resistance of many structural materials, particularly under extreme conditions of load, temperature and radiation. Here we systematically examine dislocation-particle interaction mechanisms. The analysis is based on three-dimensional discrete dislocation dynamics simulations incorporating impenetrable particles, elastic interactions, dislocation self-climb, cross-slip and glide. The core diffusion dominated dislocation self-climb process is modelled based on a variational principle for the evolution of microstructures, and is coupled with dislocation glide and cross-slip by an adaptive time-stepping scheme to bridge the time scale separation. The stress field caused by particles is implemented based on the particle-matrix mismatch. This model is helpful for understanding the fundamental particle bypass mechanisms and clarifying the effects of dislocation glide, climb and cross-slip on creep deformation.
晶体材料中的塑性变形通过位错滑移发生，而强化则通过阻碍位错运动的障碍物来实现。在相对较低的温度下，位错通过奥罗万环化、颗粒剪切、交滑移或这些机制的组合绕过颗粒。在高温下，原子扩散率变得显著，使得位错可以通过攀移过程绕过颗粒。攀移在许多结构材料的长期耐久性或抗蠕变性中起着关键作用，特别是在载荷、温度和辐射的极端条件下。在这里，我们系统地研究位错与颗粒的相互作用机制。该分析基于三维离散位错动力学模拟，其中包含不可穿透的颗粒、弹性相互作用、位错自攀移、交滑移和滑移。基于微观结构演化的变分原理对核心扩散主导的位错自攀移过程进行建模，并通过自适应时间步长方案将其与位错滑移和交滑移耦合，以弥合时间尺度分离。基于颗粒与基体的失配来实现颗粒引起的应力场。该模型有助于理解基本的颗粒绕过机制，并阐明位错滑移、攀移和交滑移对蠕变变形的影响。
