MICROSTRUCTURE-RELATED ANELASTIC AND MAGNETOELASTIC BEHAVIOR OF NANOCRYSTALLINE NICKEL

Nanocrystalline nickel was prepared by a planetary ball milling appara tus working in a vacuum of 10(-4) Pa in the 150-300 K temperature rang e. The kinetic of the milling process and the microstructure evolution upon annealing were followed by x-ray diffraction and mechanical spec troscopy measurements. It was observed that thermal annealing up to 60 0 K induces a strong reduction of the internal strains without signifi cant grain growth. Measurements of elastic energy dissipation and dyna mic elastic modulus as a function of temperature showed that in the na nocrystalline samples, anelastic relaxation processes occur, with the activation energy of grain boundary diffusion. A systematic study of t he magnetic field dependence of the dynamic modulus (Delta E effect) r evealed a correlation between the Delta E magnitude and the strain val ues obtained by x-ray diffraction analysis. (C) 1998 American Institut e of Physics. [S0021-8979(98)06119-2].