An investigation of the high-Al part of the Al–Pd–Ru phase diagram at 790–900 °C

Partial isothermal sections of the Al–Pd–Ru phase diagram at 790 and 900 °C are presented. Complex orthorhombic ɛ-phases extending from Al3Pd up to 15 at.% Ru exhibit structural variants including transient irregular structures. The Al3Pd2 phase dissolves up to 2 at.% Ru, Al13Ru4 <2.5 at.% Pd and Al2Ru up to 1 at.% Pd. A stable icosahedral quasicrystalline phase is formed around the Al71.5Pd17Ru12.5 composition. At nearby compositions two complex primitive cubic phases with a ≈ 2.0 and ≈4.0 nm were observed. These cubic phases exhibit powder X-ray diffraction (XRD) patterns very similar to that of the icosahedral phase. At compositions close to the high-Ru limit of the ɛ-range the electron diffraction patterns of complex orthorhombic structures and 1D quasicrystalline structure were revealed. At lower-Al concentrations three ternary cubic phases structurally related to quasicrystals are formed: primitive C (a ≈ 0.75 nm), bcc C1 and fcc C2 with a double lattice parameter.