Srivastava K, Weygand D, Caillard D, Gumbsch P
Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Straße am Forum 7, 76131, Karlsruhe, Germany.
Research and Development, AG der Dillinger Hüttenwerke, Werkstraβe 1, 66763, Dillingen/Saar, Germany.
Nat Commun. 2020 Oct 9;11(1):5098. doi: 10.1038/s41467-020-18774-1.
Work hardening in bcc single crystals at low homologous temperature shows a strong orientation-dependent hardening for high symmetry loading, which is not captured by classical dislocation density based models. We demonstrate here that the high activation barrier for screw dislocation glide motion in tungsten results in repulsive interactions between screw dislocations, and triggers dislocation motion at applied loading conditions where it is not expected. In situ transmission electron microscopy and atomistically informed discrete dislocation dynamics simulations confirm coupled dislocation motion and vanishing obstacle strength for repulsive screw dislocations, compatible with the kink pair mechanism of dislocation motion in the thermally activated (low temperature) regime. We implement this additional contribution to plastic strain in a modified crystal plasticity framework and show that it can explain the extended work hardening regime observed for [100] oriented tungsten single crystal. This may contribute to better understanding the increase in ductility of highly deformed bcc metals.
体心立方单晶在低同源温度下的加工硬化在高对称加载时表现出强烈的取向依赖性硬化，这是基于经典位错密度的模型所无法捕捉到的。我们在此表明，钨中螺型位错滑移运动的高激活能垒导致螺型位错之间的排斥相互作用，并在预期之外的外加加载条件下触发位错运动。原位透射电子显微镜和基于原子尺度的离散位错动力学模拟证实了排斥性螺型位错的耦合位错运动和障碍强度的消失，这与热激活（低温） regime中位错运动的扭折对机制相一致。我们在改进的晶体塑性框架中实现了对塑性应变的这一额外贡献，并表明它可以解释在[100]取向的钨单晶中观察到的扩展加工硬化 regime。这可能有助于更好地理解高度变形的体心立方金属的延展性增加。
