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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。
Compared with ordinary coarse-grained metal materials, nanocrystalline metal usually has higher strength and hardness, but its toughness is obviously reduced. In order to explore the reasons leading to the low ductility of nanocrystalline metals, the high purity and high density of coarse grains and nanocrystalline nickel sheets were studied, and their mechanical properties under uniaxial quasi-static stretching were studied by digital image correlation . By analyzing the strain field of two kinds of samples, it is confirmed that the plastic deformation of the coarse-grained nickel is uniform, while the plastic deformation of the nanocrystalline nickel shows partial shear banding. This local shear banding behavior is the leading cause of premature rupture of nanocrystalline nickel.