- Abstract Phase equilibria in Al–Pt–Ir were studied up to 50 at.% Al at 1100° C, up to 70 at.% Al at 900° C and up to 75 at.% Al at 810° C. At elevated temperatures the isostructural AlIr and high-temperature AlPt β-phases probably form a continuous compositional region. The ternary extensions of the phases Al 4 Pt, Al 21 Pt 8, Al 3 Pt 2 and low-temperature AlPt were revealed along approximately constant Al concentrations up to 15, 11, 20 and 10 at.% Ir, respectively. The Al–Ir C-phase dissolved up to 12 at.% Pt, and the χ-phase propagated up to almost Al 3 Pt. A new ternary B-phase (I4 1/acd, a= 0.86250, c= 2.18409 nm) was revealed around Al 69 Pt 7 Ir 24. Its structural model was derived from the electron diffraction data.