多晶钨纳米线拉伸变形的分子动力学模拟

Molecular dynamics simulation of tensile deformation of polycrystalline tungsten nanowire

采用分子动力学模拟方法研究不同晶粒尺寸多晶钨纳米线在拉伸过程中的应力-应变行为,详细分析晶粒尺寸对应力-应变曲线模式、弹性模量及拉伸变形机理的影响。结果表明:晶粒尺寸在(5.303~7.653)nm内的多晶钨纳米线的应力-应变曲线中存在双峰、单峰;弹性模量随晶粒尺寸的增大而增加;拉伸力学性能呈反向Hall-Petch关系;塑性变形主要在晶界处,并伴随晶粒转动;应变量达0.15时,纳米线中观察到孪晶组织;随着应变量增加,出现孪晶滑移,且孪晶附近出现局部应力集中,导致断裂。

The stress-strain behavior of polycrystalline tungsten nanowires with different grain sizes was investigated by molecular dynamics simulation.The effects of grain size on stress-strain curve mode,elastic modulus and plastic deformation mechanism were analyzed in detail.The results show that double-peak and single-peak in the stress-strain curve are found with grain sizes ranging from 5.303 to 7.653 nm.The elastic modulus increases as the grain size increases.The tensile mechanical properties exhibit a reverse Hall-Petch relationship.The plastic deformation is mainly at the grain boundary and is accompanied by the rotation of the crystal grains.When the strain reaches 0.15,twinning structure is observed.As strain increases,twinning slip occurs and local stress concentration arises near the twin boundaries,resulting in breakage.