Solid state phase equilibria and intermetallic compounds of the Al–Cr–Ho system

The solid state phase equilibria of the Al–Cr–Ho ternary system at 500 °C were experimentally investigated. The phase relations at 500 °C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al11Cr2, Al11Cr4 and Al17Ho2 were not found at 500 °C. Crystal structures of Al9Cr4 and Al8Cr4Ho were determined by the Rietveld X-ray powder data refinement. Al9Cr4 was found to exhibit cubic structure with space group I4̄3m (no. 217) and lattice parameters a=0.9107(5) nm. Al8Cr4Ho crystallizes in ThMn12 structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al4Cr phase in this work should be μ-Al4Cr by comparing with XRD pattern of the hexagonal μ-Al4Mn compound.