中文摘要：

运用分子动力学模拟方法研究了不同尺寸多晶镍纳米线在受拉过程中的塑性变形行为,详细分析了多晶镍纳米线直径尺寸对其流变应力以及塑性变形机制的影响。从模拟结果中可以看出,在多晶镍纳米线受拉产生变形的过程中,晶界滑移主导晶间变形机制,位错形核滑移主导晶内变形机制。随着多晶镍纳米线半径的增加,平均流变应力逐渐增加,但增幅趋于平缓。这是由于径向分布的晶粒个数随着纳米线直径的增加而增加,限制了晶界的滑移,使更多的位错形核于晶界,在滑移扩展过程中相遇发生堆积缠绕,进而对纳米线产生强化作用。位错密度随纳米线直径的增加增幅逐渐降低,导致了流变应力增幅趋于平缓。

英文摘要：

The deformation mechanisms and tensile behavior of polycrystalline Ni nanowires with various diameters were investigated by molecular dynamics simulation. The results showed that grain boundary sliding and dislocation activities dominated the inter-and intra-granular deformation respectively.With the increase of nanowire diameter,the averaged flow stress increased gradually while the increase amplification decreased. Such a result could be attributed to the increased number of grains along the radial direction,which applied more constraints on grain boundary sliding,and then promoted more dislocation nucleating from grain boundaries. These dislocations tangled with each other forming pileups during propagation,and hence strengthened the nanowires.The reducing increase amplification of average stress could be attributed to the reduction of dislocation density increasement in nanowires with increasing diameter.