Quantitative microstructural evolution and the corresponding microhardness of electrodeposited nanostructured nickel sheet during cold rolling deformation are investigated by x-ray diffraction, transmission electron microscopy and Vicker’s microhardness testing. Particularly, to investigate the effect of stress states on deformation behavior, two series of gradient nanostructured nickel with symmetric structures and the homogeneous counterparts with three levels of grain size are compared based on macro-statistical data. In such hierarchical sandwich-like gradient samples, the layers with larger grain size, as the soft phase, indeed sustain more deformation. Deformation-induced grain rotation changes are observed in the center layers with a relatively larger grain size, accompanied by an obvious decrease in microhardness. According to the quantitative microstructural parameters including the grain size, dislocation density and stacking fault probability before and after deformation, evaluation based on Hall-Petch and Bailey-Hirsch relationships indicates the transition from strain hardening to softening can be attributed to grain orientation change.

中文翻译：

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电沉积梯度纳米结构镍在冷轧变形过程中的晶粒取向诱导软化

通过X射线衍射，透射电子显微镜和维氏显微硬度试验研究了电沉积纳米结构镍薄板在冷轧变形过程中的定量显微组织演变和相应的显微硬度。特别地，为了研究应力状态对变形行为的影响，基于宏观统计数据，比较了两个具有对称结构的梯度纳米结构镍系列和具有三个晶粒尺寸的均质对应物。在这种分层的三明治状梯度样品中，具有较大晶粒尺寸的层（作为软相）的确承受更大的变形。在具有相对较大晶粒尺寸的中心层中观察到由变形引起的晶粒旋转变化，同时显微硬度明显降低。