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通过直流电沉积制备平均晶粒度为27.2nm,宽晶粒尺寸分布(10～120nm)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。
Nanocrystalline nickel (B-NC-Ni) with average grain size of 27.2 nm and wide grain size distribution (10-120 nm) was prepared by direct current deposition. In the tensile test of B-NC-Ni, there are two different types of engineering stress-strain curves and macroscopic fractures. The results show that the complete tensile curve is the intrinsic curve with the stage of constant stress deformation and the macroscopic fracture is cut . The incomplete tensile curve has been broken before the platform appears. It is mainly due to the fact that the cathodic precipitation of H during electrodeposition may cause the formation of vacancies and micropores in the coating, both of which will aggravate the formation of cracks on the grain boundaries during deformation , Macroscopic fracture was normal off. In addition, the influence of impurities S (0.015%, mass fraction, the same below) on the tensile properties of B-NC-Ni in the experiment can be neglected.