BCC金属中空穴生长的Finnis-Sinclair势分子动力学模拟
Void Growth in BCC Metals Simulated with Molecular Dynamics using the Finnis-Sinclair Potential
摘要：
韧性金属的断裂过程包括孔洞的形核、生长和连接。这一过程既发生在典型的工程应用中所涉及的低速率下，也发生在与动态断裂过程（如破裂）相关的高速率下。本文采用基于Finnis-Sinclair原子间相互作用势的分子动力学（MD）方法，研究了体心立方（bcc）金属V、Nb、Mo、Ta和W在单晶中空穴的高速生长。Finnis-Sinclair势的使用使得能够在室温和应变速率从10^9/s下降到10^6/s以及高达1.28亿个原子的系统下，在原子水平上研究与空穴生长相关的塑性。观察到的原子系统经历了一个过渡，从孪生在这个范围的高端在低端的位错流。我们分析了模拟的具体机制，塑性与空洞生长的位错环冲压出来，以适应日益增长的空洞。我们还分析了在不同应变速率下模拟纳米晶Ta膨胀时空洞的形核和长大过程。我们评论的差异，在体心立方金属与空洞生长的塑性相比，在面心立方（fcc）金属早期的研究。
英文摘要：
The process of fracture in ductile metals involves the nucleation, growth, and linking of voids. This process takes place both at the low rates involved in typical engineering applications and at the high rates associated with dynamic fracture processes such as spallation. Here we study the growth of a void in a single crystal at high rates using molecular dynamics (MD) based on Finnis-Sinclair interatomic potentials for the body-centred cubic (bcc) metals V, Nb, Mo, Ta, and W. The use of the Finnis-Sinclair potential enables the study of plasticity associated with void growth at the atomic level at room temperature and strain rates from 10^9/s down to 10^6/s and systems as large as 128 million atoms. The atomistic systems are observed to undergo a transition from twinning at the higher end of this range to dislocation flow at the lower end. We analyze the simulations for the specific mechanisms of plasticity associated with void growth as dislocation loops are punched out to accommodate the growing void. We also analyse the process of nucleation and growth of voids in simulations of nanocrystalline Ta expanding at different strain rates. We comment on differences in the plasticity associated with void growth in the bcc metals compared to earlier studies in face-centred cubic (fcc) metals.
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