New approximant phases in Al–Cr–Fe

Recently, new approximant phases were pointed out in the Al–Cr–Fe system, namely orthorhombic O-Al–Cr–Fe, hexagonal H-Al–Cr–Fe and monoclinic M-Al–Cr–Fe. In the corresponding analysed samples, the new approximant phases were always coexisting with metallic aluminium. We have studied the Al–Cr–Fe system within a broad composition range. In one alloy with composition Al81Cr11Fe8, two new crystalline approximants of the decagonal phase were discovered. These phases were analysed by differential thermal analysis (DTA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and microprobe analysis. The phases were found to be isomorphic with a C3,I-phase earlier discovered by Van Tendeloo et al. in Al–Mn–Ni and an O1-phase earlier discovered by Dong et al. in Al–Cr–Cu–Fe. Moreover, we have found in the same sample the O-Al–Cr–Fe phase as well as metallic aluminium.