XRD and HREM studies from the decomposition of icosahedral AlCuFe single-phase by high-energy ball milling

In this investigation the Al64Cu24Fe12 alloy was melted in an induction furnace and solidified under normal casting conditions. In order to obtain the icosahedral phase (i-phase) in a single-phase region, the as-cast sample was subject to a heat treatment at 700 °C under argon atmosphere. Subsequently, the i-phase was milled for different times in order to evaluate phase stability under heavy deformation. X-ray diffraction (XRD) and high-resolution electron microscopy (HREM) analysis were conducted to the structural characterization of ball-milled powders. XRD results indicated a reduction in quasicrystal size during mechanical ball milling to about 30 h. HREM analysis revealed the presence of aperiodic nano-domains, for example, with apparent fivefold symmetry axis. Therefore, the i-phase remains stable over the first 30 h of ball-milling time. However, among 30–50 h of mechanical milling the i-phase transforms progressively into β-cubic phase.

► Point defects induced during milling leading to an order–disorder quasicrystal transition.
► Nanoquasicrystalline regions of 12 nm are obtained.
► Highly ordered i-phase with high symmetry transforms to a crystalline phase of intermetallic character and lower symmetry.