On the constitution of Al−Pt−(Pd or Ni) around 50 at.% Al

A series of Al−Ni−Pt and Al−Pd−Pt alloys containing ∼50 at.% Al were studied by powder X-ray diffraction, differential thermal analysis and scanning electron microscopy. The formation of a rhombohedral β’-phase by cooling is interpreted as evidence of the existence of a high-temperature β-phase of the CsCl-type structure. It is argued that in binary Al−Pt this structure is stable at equiatomic composition and elevated temperatures rather than that of the FeSi-type structure.

► Al−Ni−Pt and Al−Pd−Pt alloys containing ∼50 at.% Al were studied. ► At ternary compositions the rhombohedral β’-phase is metastable. ► The β’-phase is formed from a high-temperature β-phase of the CsCl-type structure. ► The B2 rather than B20 structure is stable at AlPt at elevated temperatures.