Determination of RuAl phase boundaries in binary Ru-Al phase diagram at room temperature and 1200°C

Binary Ru-Al alloys with nominal compositions from 29.39 at.% Al up to 60.47 at.% Al were manufactured by powder-metallurgy processing. Single-phase RuAl with a homogeneous microstructure was prepared which is difficult to achieve by melting metallurgy. The microstructure and lattice parameters of the alloys were investigated by optical and scanning electron microscopy, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy and X-ray diffraction. The parametric method was employed to determine the RuAl phase boundaries. Single-phase RuAl was found to exist from near-stoichiometry up to 53.8 at.% Al at room temperature and up to 54.5 at.% Al at 1200 degrees C, respectively. In addition, the phase Ru2Al3 was found to be stable at room temperature and to have a very narrow range of stoichiometry.