Published online by Cambridge University Press: 26 February 2011
The amorphization reaction in mechanically prepared metallic Ni-Zr composites has been investigated by X-ray diffraction, electrical conductivity and magnetization measurements during isothermal annealing. The formation kinetics of the amorphous phase are determined by the diffusion of the Ni atoms across the amorphous NiZr layer. The diffusivity of Ni atoms in the initially formed amorphous Ni58.5 Zr41.5 is measured in the temperature range from 225°C (Dni= 5.3×10−17 cm2/sec) to 325°C (Dni= 1×10−14 cm2/sec). The data fit an Arrhenius plot with an activation energy of 1.4 eV. Magnetic coercivity measurements indicate that neither recovery nor recrystallization occurs in the Ni layers during the reaction. The Kirkendall effect caused by the anomalous fast diffusion of Ni is directly monitored by dilatometric measurements. Microhardness results are also presented. The role of a diffusion-related growth selection favoring the amorphous phase is critically assessed with respect to the glass formation.