Understanding plastic deformation of crystals in terms of the fundamental physics of dislocations has remained a grand challenge in materials science for decades. To overcome this, the Discrete Dislocation Dynamics (DDD) method has been developed, but its lack of atomistic resolution leaves open the possibility that certain key mechanisms may be overlooked. By comparing large-scale Molecular Dynamics (MD) with DDD simulations performed under identical conditions we uncover significant discrepancies in the predicted strength and microstructure evolution in BCC crystals under high-strain rate conditions. These are traced to unexpected behaviors of dislocation network nodes forming at dislocation intersections, that can move in ways not previously anticipated as revealed by MD. Once these newfound freedoms of nodal motion are incorporated, DDD simulations begin to closely match plastic evolution observed in MD. This additional mechanism of motion whereby non-screw dislocations can change their glide plane profoundly affects fundamental processes of dislocation multiplication, recovery and storage that define strength of metals.

中文翻译：

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位错网络节点的增强活动性及其对位错倍增和应变硬化的影响

几十年来，从位错的基本物理角度理解晶体的塑性变形一直是材料科学中的一个巨大挑战。为了克服这个问题，人们开发了离散位错动力学（DDD）方法，但其缺乏原子分辨率，导致某些关键机制可能被忽视。通过将大规模分子动力学 (MD) 与在相同条件下进行的 DDD 模拟进行比较，我们发现高应变率条件下 BCC 晶体的预测强度和微观结构演变存在显着差异。这些可以追溯到位错交叉点处形成的位错网络节点的意外行为，这些节点可以按照 MD 揭示的先前未预期的方式移动。一旦结合了这些新发现的节点运动自由度，DDD 模拟就开始与 MD 中观察到的塑性演化紧密匹配。这种非螺旋位错可以改变其滑移面的附加运动机制深刻地影响了定义金属强度的位错增殖、恢复和存储的基本过程。