多晶钨韧脆转变的原子级指标：铼和温度对裂纹尖端塑性的影响
Atomistic Indicators of the Ductile-to-Brittle Transition in Polycrystalline Tungsten: Temperature and Rhenium Effects on Crack-Tip Plasticity
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中文总结 AI 辅助
该研究通过分子动力学模拟，探究温度和铼含量对多晶钨裂纹尖端塑性的影响，揭示了高应变速率下韧脆转变的原子级指标，为理解体心立方金属的断裂行为提供了依据。
中文摘要 AI 辅助
体心立方钨的断裂响应由裂纹尖端失稳与位错介导的塑性适配之间的竞争决定。采用分子动力学（MD）模拟，在应变速率为5×10^8 s^-1、温度范围300-1800 K下，对带边裂纹的多晶W及W-Re合金施加位移控制的I型拉伸载荷进行研究。加热纯W会降低失稳应力、有效试样刚度及失稳前体积功密度，而失稳应变则相对分散。从失稳前功导出的归一化功损失度量给出了宽的S型转变标记T*_MD≈870 K，该标记是模拟几何结构和高应变速率加载条件的特征。在现有W-Re成分中，W-10Re在大多数温度下比纯W表现出更大的失稳前变形和功积累，而最大应力响应仍强烈依赖温度和成分。保留的位错特征和尖端附近活性的变化表明，Re改变了裂纹尖端的塑性适配路径，而非仅产生简单的强度提升。Common-state分析进一步显示，Re改变了保留的1/2<111>线特征和裂纹尖端附近位错活性的时间分布，并未均匀增加局部位错数量。这些力学和缺陷结构的耦合变化提供了高应变速率韧脆转变（DBT）的原子级指标，但无法直接预测实验韧脆转变温度（DBTT）。独立的OpenDiS/pydis计算表明，无裂纹多晶W中存在类源的弓出和异质位错网络发展，提供了介观尺度的背景，未暗示MD-DDD的直接定量耦合。
英文摘要
The fracture response of body-centered-cubic tungsten is governed by competition between crack-tip instability and dislocation-mediated plastic accommodation. Molecular dynamics (MD) simulations are used to examine edge-cracked polycrystalline W and W-Re under displacement-controlled Mode-I tension from 300-1800 K at a strain rate of 5 x 10^8 s^-1. Heating pure W reduces the instability stress, effective specimen stiffness, and pre-instability volumetric work density, while the instability strain remains comparatively scattered. A normalized work-loss metric derived from the pre-instability work gives a broad sigmoid crossover marker, T*_MD ~ 870 K, characteristic of the simulated geometry and high-rate loading conditions. Among the available W-Re compositions, W-10Re shows greater pre-instability deformation and work accumulation than pure W across most temperatures, while the maximum-stress response remains strongly temperature- and composition-dependent. Changes in retained dislocation character and near-tip activity indicate that Re modifies the crack-tip plastic-accommodation pathway rather than producing a simple strength increase. Common-state analysis further shows that Re alters the retained 1/2<111> line character and the temporal distribution of near-tip dislocation activity without uniformly increasing the local dislocation population. These coupled mechanical and defect-structure changes provide atomistic indicators of a high-rate ductile-to-brittle transition (DBT), but not a direct prediction of experimental DBTT. A separate OpenDiS/pydis calculation demonstrates source-like bow-out and heterogeneous dislocation-network development in crack-free polycrystalline W, providing mesoscale context without implying direct quantitative MD-DDD coupling.
