超薄Ni/Ni_3Al(001)纳米线力学性能和晶体缺陷拉压不对称性研究(英文)

Tension-Compression Asymmetry in Mechanical Behavior and Crystal Defect of Thin Ni/Ni_3Al(001) Nanowires

利用分子动力学方法研究超薄Ni/Ni3Al(001)纳米线力学性能和晶体缺陷的拉压不对称,对应力-应变曲线和晶体曲线在不同的温度下进行比较。模拟表明在拉伸载荷作用下不全位错的施密特因子大于压缩载荷下的施密特因子,在10 K温度下的流变应力行为异常,同时超薄Ni/Ni3Al(001)纳米线在不同温度下都表现为抵抗压缩载荷能力比拉伸载荷强。结果显示超薄Ni/Ni3Al(001)纳米线具有显著的拉伸不对称特性。此外,堆积层错提高原子移动,不全位错从堆垛层错处发射。在促进位错发射过程中原子移动扮演着重要的角色;而且在拉-压载荷下不同晶体缺陷主要是点位错和层错,层错主要发生在4个{111}方向。研究拉压不对称与温度之间的关系,可以更准确和全面的理解超薄Ni/Ni3Al(001)纳米线的力学性能。

Molecular dynamics （MD） simulations were employed to study the asymmetry in mechanical behavior and crystal defect of thin Ni/Ni3Al （001） nanowires （NWs） under tension and compression. The stress-strain responses and crystal defects of the thin Ni/Ni3Al （001） NWs were compared at different temperatures. The simulation results indicate that the Schmidt factor of the leading partial dislocation under tensile loading condition is larger than that under compression. The flow stress presents abnormal behavior at 10 K under compression. The thin Ni/Ni3Al （001） NW is stronger in compression than in tension at different temperatures. These results present significant tension-compression asymmetry. In addition, the stacking faults enhance atomic shuffling and a partial dislocation is emitted from the stacking fault. Atomic shuffling plays an important role in stimulating the dislocation emission. Furthermore, we also have found that the evolution of different crystal defects is mainly point dislocations and stacking faults. The thin Ni/Ni3Al （001） NWs give rise to stacking faults on all four possible {111} orientations under tension and compression. Generally, studying of the relation between the tension-compression asymmetry and the temperature of thin Ni/Ni3Al （001） NWs at different temperatures can help us further understand the mechanical properties accurately and completely.