Kinetics of the crystallization of icosahedral phase in ultra thin deposits of Al₆₂Cu_25.5Fe_12.5 alloy

Abstract

Made at room temperature, the deposition of the three elements Al, Cu, Fe in the atomic proportion 62/25.5/12.5 allows amorphous deposits to be obtained. The mixture becomes crystalline when subjected to heat treatment. Several deposits made on transmission electron microscopy (TEM) grids were heated up to different temperature thresholds. Only during annealing above 723 K were nucleation and growth of i-AlCuFe observed. A Mehl–Johnson–Avrami model is proposed to describe this crystallization. This model fits the experimental data very well and allows mean activation energies for volume diffusion to be calculated. Assuming the time of the total transformation, a TTT curve is plotted. Nucleation density values and activation energy of the i-Al₆₂Cu_25.5Fe_12.5 phase nucleation are estimated.