New approximant phases in Al-Cr-Fe

Recently, new approximant phases were pointed out in the Al-Cr-Fe system, n amely 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 sys tem within a broad composition range. In one alloy with composition Al81Cr1 1Fe8, two new crystalline approximants of the decagonal phase were discover ed. These phases were analysed by differential thermal analysis (DTA), tran smission electron microscopy (TEM), scanning electron microscopy (SEM) and microprobe analysis. The phases were found to be isomorphic with a C-3.1-ph ase earlier discovered by Van Tendeloo et al. in Al-Mn-Ni and an O-1-phase earlier discovered by Dong et al. in Al-Cr-Cu-Fe. Moreover, we have found i n the same sample the O-Al-Cr-Fe phase as well as metallic aluminium. (C) 2 000 Elsevier Science B.V. All rights reserved.