电沉积宽晶粒尺寸分布纳米镍的本征拉伸行为

Intrinsic Tensile Behavior of Electrodeposited Nanocrystalline Ni with a Broad Grain Size Distribution

摘要:

通过直流电沉积制备平均晶粒度为27.2 nm，宽晶粒尺寸分布(10~120 nm)的纳米镍(B-NC-Ni)。在B-NC-Ni的拉伸实验中，存在着两类不同的工程应力-应变曲线及宏观断口，结果表明：完整的拉伸曲线即本征曲线，具有恒应力变形阶段，宏观断口呈切断；而不完整的拉伸曲线在平台出现之前已发生断裂，主要是由于电沉积时阴极析出的H可能会使镀层形成空位和微孔两类缺陷，均会加剧变形时晶界上裂纹的形成，宏观断口呈正断。此外，实验中杂质S(0.015%, 质量分数, 下同)对B-NC-Ni的拉伸性能影响可忽略

Abstract:

Nanocrystalline Ni with a mean grain size of 27.2 nm and a broad grain size distribution ranging from 10 nm to 120 nm (B-NC-Ni) was prepared by direct current electrodeposition. In tensile experiments of B-NC-Ni, there are two types of engineering stress-strain curves and macroscopic fracture. Results reveal that a complete tensile curve, i.e. an intrinsic curve, possesses a constant stress deformation stage, and macrofracture is shear; a incomplete tensile curve shows premature plastic instability before the appearance of the flat plastic region, mainly because in the process of nickel deposition, flaws including vacancies and porosity may form in the deposit due to the cathode hydrogen evolution, resulting in more serious crack formation at the grain boundary during deformation, and the fracture is vertical shear. In addition, the effect of S impurities (0.015 wt%) on tensile properties can be neglected in the present work