Metastable microstructures in laser-ablation-deposited AlFe thin films

Abstract

Abstract The paper reports studies on the nature of metastable microstructure evolved during pulsed-laser-ablated thin films of Al–Fe alloys with Al72Fe28 and Al40Fe60 average compositions. The microstructure of these films consists of vapourplasma-quenched matrix and solidified liquid droplets of various sizes embedded in the matrix. For both alloy compositions, vapour quenching yields an amorphous phase. The microstructure of the embedded droplets exhibits size dependence. In Al72Fe28 films, a hierarchy of structures from amorphous to metastable nanosized bcc to bcc with ordered ω precipitate was observed as a function of increasing size. The formation of ordered ω phase is a new observation. The sequence of structure evolution of droplets in Al40Fe60 films with increasing size was found to be amorphous to metastable bcc to ordered B2. We argue that disorder trapping occurs during solidification of these droplets.