温度对V金属拉伸力学性能影响的分子动力学研究

Molecular Dynamics Investigation of Temperature Effect on Tensile Mechanical Property of Vanadium Metal

  • 摘要: 本文通过分子动力学方法模拟研究V金属拉伸力学性能,从原子尺度深入探讨300、600、900和1 200 K 4种温度对其拉伸力学性能的影响机制。结果表明,随着温度的升高,V金属的抗拉强度逐渐减小,这与相变以及位错的形核和运动密切相关。在拉伸过程中,材料的塑性变形由相变主导,位错形核和运动在材料的断裂机制中起主导作用。在弹性变形阶段,由BCC(体心立方)结构原子向FCC(面心立方)结构原子和other(无法识别的其他晶格)结构原子转变为主导。并且由于V金属的各向异性,other结构原子逐渐向特定晶面聚集形成相互交叉的条带状结构,高能量原子的聚集为位错提供有利的形核位点,促进位错形核,位错附近自由原子体积更大,为变形贡献更大的应变量,体系原子向能量更低、更稳定的状态转变,发生FCC和other结构向BCC结构的逆转变,最终各结构原子数量趋于平缓。随着温度的升高,原子振动频率和振动幅度增大,相变更容易进行,相变开始提前,且持续时间延长,分布状态转变的临界点延迟,导致应力的下降被推迟。基于位错定量分析发现,占比最大的是1/2〈111〉位错,同时随着温度的升高位错的出现时间被延迟,材料达到抗拉强度之后应力的下降减缓。本文通过对V金属拉伸性能原子尺度的深入分析,揭示温度对其拉伸性能的影响并阐明其变形机制,为后续V及V合金的研究提供科学参考。

     

    Abstract: This study investigated the influence of temperature on the tensile mechanical properties of vanadium (V) metal at the atomic scale. Molecular dynamics simulations were performed to analyze the tensile behavior under four different temperatures: 300, 600, 900, and 1 200 K. The simulations were conducted under three-dimensional periodic boundary conditions, with the atomic model initially optimized for energy minimization using the conjugate gradient algorithm. The isothermal-isobaric (NPT) ensemble was employed to simulate uniaxial tensile deformation along the y-axis with a strain rate of 0.004 ps−1. Temperature and pressure were controlled using the Nose-Hoover thermostat and barostat methods, with damping parameters set to 0.1 ps for temperature and 1.0 ps for pressure. The entire simulation unit had a total of 750 000 atoms. To investigate its microscopic deformation mechanisms, this study used common neighbor analysis (CNA) and dislocation analysis, combined with Python scripts to quantitatively process the analysis results. The results demonstrate that the tensile strength of V metal gradually decreases with increasing temperature, which is closely associated with phase transformation, as well as dislocation nucleation and motion. During tensile deformation, plastic deformation is primarily governed by phase transformation, while dislocation nucleation and motion play a dominant role in the fracture mechanism. In the elastic deformation stage, the transformation of atoms from the body-centered cubic (BCC) structure to the face-centered cubic (FCC) and other (unrecognized lattice) structures predominates. Owing to the anisotropy of V, atoms with other structures gradually aggregate on the specific crystal planes. The accumulation of high-energy atoms provides favorable nucleation sites for dislocations, promoting dislocation nucleation. Dislocation analysis reveals that the 1/2\langle 111 \rangle dislocation is the most predominant. Moreover, with increasing temperature, the emergence of dislocations is delayed, and the stress drop after the tensile strength is mitigated. Through an in-depth atomic-scale analysis of the tensile properties of V metal, this study elucidates the effect of temperature on its tensile performance and clarifies the deformation mechanisms, providing scientific insights for subsequent research on V and V-based alloys.

     

/

返回文章
返回