孔洞缺陷对α-Fe拉伸变形行为影响的分子动力学模拟

Molecular Dynamics Simulation of the Effects of Void Defect on the Tensile Deformation Behavior of α-Fe

摘要:

为深入研究孔洞缺陷对α-Fe试样拉伸变形行为的影响，构建含不同大小孔洞缺陷的α-Fe试样计算模型，并进行单轴拉伸应变下的分子动力学模拟。结果表明：整体趋势上，含孔洞缺陷试样的拉伸力学性能损减与孔洞尺寸正相关，孔洞尺寸越大，试样越容易进入塑性变形阶段；含孔洞缺陷试样的杨氏模量、屈服应力、极限强度和拉断延伸率均随着孔洞半径的增大而减小；试样的塑性变形表现为拉伸应力诱发的相变和位错滑移混合的机制；随着孔洞半径的增大，试样的应力-应变曲线特征发生显著变化——试样的塑性屈服段和应变硬化段越来越短，应变硬化段甚至消失。研究有助于深入认识孔洞缺陷对金属变形机制的影响，为后续开展多晶α-Fe材料的物理和力学性质的分析研究奠定有益基础。

Abstract:

To further investigate the effects of void defect on the plastic deformation behavior of α-Fe under tensile load, the molecular dynamic models of the α-Fe samples with the void defects were established and related simulations under uniaxial tension were carried out for a series of models. The results show that overall, the deterioration of tensile mechanical properties of the sample with void is positively related to the void size. The larger the void size, the easier the occurrence of plastic deformation stage for sample. Overall, the Young's modulus, yield stress, ultimate tensile strength and tensile elongation of the samples containing void decrease with increasing the radius of void. The plastic deformation mechanism is of a mixture of the tensile stress-induced structural phase transition and the dislocation slip. However, the characteristics of stress-strain curves change significantly with increasing the radius of void, the plastic yield stage and strain hardening stage of the sample become shorter, and the strain hardening stage even vanishes. The research deepens the understanding of the effects of void defect on the mechanical properties and plastic deformation mechanisms of metals and lays a useful foundation for the subsequent analysis and study of the physical and mechanical properties of polycrystalline α-Fe materials under various conditions.