Structure and mechanical behaviour of Al–Fe–X and Al–Ni–X rapidly solidified alloys

Abstract

Amorphous and nanostructured Al-based alloys have seen increased potential for technological application during recent years. Nanostructured Al-based alloys, composed of α-Al nanograins embedded in an amorphous matrix, are frequently produced by crystallisation of an amorphous precursor phase. It was observed that the ductile–brittle behaviour of a metallic amorphous phase depends on its chemical composition. Therefore, the knowledge of the interactions between the components in the liquid state is important for the glass forming ability and for the short range order of the amorphous phase. In order to enhance the understanding of the interactions and the subsequent structure, both Al–Fe–X and Al–Ni–X series of alloys were produced by rapid solidification and studied. The structure was characterised by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). Al clusters with a medium range order up to 2 nm were observed in an amorphous Al–Fe–Nb alloy. It is proposed that the kind of cluster formed in the liquid state can control the glass forming ability and induce the formation of a heterogeneous amorphous phase. The presence of Fe and Nb increased the microhardness of the Al-based alloys.