Grain growth kinetics in nanostructured nickel

Grain growth kinetics for nanostructured nickel was studied by means of isothermal and isochronal annealing and TEM. The range of temperature for the isothermal and isochronal annealing has been selected between 603K and 683K. The isothermal curves for grain size show that an explosive grain growth occurs in the early stage of annealing, but the growth returns normal beyond gain size of 600 nm. The change in microstructure in the annealed specimens has been investigated by TEM. The activation energy for the grain growth was found to be 102 kJ/mol from the plot of grain growth rate vs. 1/T, which is comparable to the activation energy for diffusion at the grain boundaries. The time exponent was obtained from the plot of grain size difference vs, annealing time, and found to be in the range of 1/6-1/7. (C) 2000 Acta Metallurgica Inc.