中文摘要：

和普通粗晶金属材料相比,纳米晶体金属通常具有较高的强度和硬度,但其韧性明显降低。为了探究导致纳晶金属低韧性的原因,以高纯度、高致密度的粗晶和纳晶金属镍片为研究对象,利用数字图像相关技术研究了其在单轴准静态拉伸下的力学性能。通过分析2种试样的应变场证实,粗晶镍的塑性变形是均匀的,而纳晶镍的塑性变形表现出局部剪切带化。这种局部剪切带化行为是导致纳晶镍过早断裂的主要原因。

英文摘要：

Compared with ordinary coarse-grained metals,the nanocrystalline metals exhibit higher strength and hardness,but have a decrease in ductility.To investigate the reasons of low ductility in nanocrystalline metals,contrastive study of mechanical behaviors between high purity,fully dense coarse-grained Ni sheets and nanocrystalline Ni sheets was carried out under uniaxial quasi-static tensile loading through digital image correlation method in this paper.From the displacement and strain fields of the two sorts of samples,uniform plastic deformation was observed in the coarse-grained Ni sample.Whereas,the nanocrystalline Ni exhibited shear localization in the form of shear band,which is the main reason of the early failure during plastic deformation in nanocrystalline Ni.