ABSTRACT

The micromechanism-based stepwise strain hardening behaviour of copper single crystals significantly depends on the competition and collaboration between dislocation slip and deformation twinning. A crystal plasticity-based model of the strain hardening characteristics associated with slip and twinning interactions is proposed that focuses on modelling the stepwise strain hardening behaviour. An accumulated twin volume fraction is incorporated into the evolution of slip resistance to model slip–twinning (S-T) interactions at small strains. Then, the following stress fluctuation stage caused by the crystal reorientation is related to the twinning–twinning (T-T) interactions. Upon deformation to a large strain, a saturated hardening law including the slip–slip (S-S) interactions in the twinned region and the accumulated slip are presented. The effects of the initial crystal orientation and twinning on distinguished hardening stages are investigated. The stepwise strain hardening model reveals the dominating hardening mechanism at the initial hardening stage, which has been identified for orientation-dependent copper single crystals by investigating the slip and twinning increments. The stress fluctuation of a copper single crystal with a particular grain orientation can be described by introducing the evolution of the twin volume fraction and its saturation value, which allows an in-depth understanding of the evolution of large plastic deformation.

摘要

基于微力学的铜单晶逐步应变硬化行为很大程度上取决于位错滑移和变形孪晶之间的竞争与协同作用。提出了基于晶体塑性的与滑移和孪生相互作用相关的应变硬化特性模型，该模型着重于对逐步应变硬化行为进行建模。在小应变下，累积的孪晶体积分数被纳入到抗滑性演化过程中，以模拟模型中的双绞线（ST）相互作用。然后，由晶体重新取向引起的随后的应力波动阶段与孪晶-孪晶（TT）相互作用有关。在变形为大应变后，出现了饱和硬化定律，包括孪生区域中的滑移-滑移（SS）相互作用和累积的滑移。研究了初始晶体取向和孪晶对明显的硬化阶段的影响。逐步应变硬化模型揭示了初始硬化阶段的主要硬化机制，该机制已通过研究滑移和孪生增量确定了与取向有关的铜单晶。可以通过引入孪晶体积分数及其饱和值的演变来描述具有特定晶粒取向的铜单晶的应力波动，从而可以深入了解大塑性变形的演变。通过研究滑移和孪生增量，已经确定了与取向有关的铜单晶。可以通过引入孪晶体积分数及其饱和值的演变来描述具有特定晶粒取向的铜单晶的应力波动，从而可以深入了解大塑性变形的演变。通过研究滑移和孪生增量，已经确定了与取向有关的铜单晶。可以通过引入孪晶体积分数及其饱和值的演变来描述具有特定晶粒取向的铜单晶的应力波动，从而可以深入了解大塑性变形的演变。