Abstract: During the last decade, considerable attention is paid to nanocrystalline materials for their unique mechanical, physical,and chemical properties. High frequency pulse current and strong electrolyte flushing are employed to electrodeposit nanocrystalline nickel without any additives. Moreover, the effects of the grains sizes on the mechanical properties of nanocrystalline nickel are examined. It is found that the properties of the deposited nickel such as tensile strength are improved substantially with the decrease of the grain size at room temperature. The tensile strength of nickel is improved when the grain size decreased from 1 000 nm to 70 nm, at which the maximum tensile strength of 1 160 Mpa is observed. However, with the further refinement of crystal grain, the tensile strength of nickel reduces. It indicates the deviation of tensile strength from Hall-Petch relationship for nanocrystalline nickel while the grain sizes are less than 70 nm. Unlike the tensile strength at room temperature and 200 ℃, the tensile strength of nanocrystalline nickel at 400 ℃ approximately keeps constant in the range of crystal grain from 50 nm to 1000 nm.

Key words: Electrodeposition, materials, Mechanical properties, Nanocrystalline, Precision electroforming