Non-isothermal kinetic studies of crystallization in amorphous Al 86 Ni 10 MM 4 alloy

Al86Ni10MM4 (MM: Mischmetal) amorphous ribbons were prepared by melt spinning on a child copper wheel. Non-isothermal crystallization kinetics of the amorphous alloy was studied by differential scanning calorimetry (DSC). The crystallized phases were determined by X-ray diffraction method and transmission electron microscopy. DSC traces were analyzed by Kissinger method to determine the apparent activation energy of crystallization. Changes in the activation energy (Eα) with progression of crystallization were also evaluated by differential iso-conversional method of Friedman. For the precipitation of nanometer-sized Al particles, the activation energy slightly increased with increasing the conversion fraction up to α=0.2, but remained almost constant until α=0.8. Because of the solute enrichment around the particles in the matrix, higher values of Eα were obtained at the late stage of crystallization. Results of nano-indentation test also showed a significant improvement in the hardness of the ribbons due to the formation of fcc-Al nanoparticles.