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

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

Key words:nanocrystalline Ni; tensile behavior; cathode hydrogen evolution; electrodeposition