粗晶与纳晶镍片拉伸力学行为

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。

Tensile Mechanical Behaviors between Coarse-Grained Ni Sheets and Nanocrystalline Ni Sheets

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.