Microstructural and mechanical property evolution in cold-rolled electrodeposited nanocrystalline nickel.

摘要

The goal of the present study was to determine the effect of cold-rolling on microstructural and mechanical properties in electrodeposited nanocrystalline nickel with an average grain size of approximately 29 nm. Samples were cold-rolled to strains of up to 80% elongation without signs of failure. Microstructural changes were evaluated using XRD and TEM while mechanical property evolution was investigated via microhardness and tensile testing.Average grain size and crystallographic texture were found to remain relatively unchanged after cold-rolling. Similarly, hardness remained constant after a small initial increase. Tensile testing results showed relatively constant strain hardening coefficients and an increase in yield strength (sigma y), ultimate tensile strength (sigmaUTS), and fracture stress (sigmaf). A marked decrease in fracture strain (epsilon f) was noted, attributed to the possible development of cavitation in the microstructure. Grain boundary sliding and/or rotation are proposed as the dominant deformation mechanisms active in nanocrystalline nickel during cold-rolling.