ROLE OF AN INTERGRANULAR PHASE IN RUAL WITH SUBSTITUTIONAL ADDITIONS

The unusual room-temperature ductility of the binary RuAl (B2) phase i s extended by the occurrence of an intergranular eutectic film in a ma nner seemingly akin to a compliant layer effect. The premise that the controlled deployment of such a film might extend the favourable mecha nical properties of RuAl to ternary formulations was examined for subs titutional additions of Ni, Co and Ti in RuAl. Whereas single-phase te rnary formulations invariably resulted in a sharp loss of ductility, d ual-phase alloys in the pseudo-binary series Ru50Al50-Co70Al30 and Ru5 2Al48-Ru52Ti48 were found to support significant plasticity, as determ ined by room-temperature compression tests, up to alloying additions o f the order of 40 at.%. Alloys based on the series Ru50Al50-Ni65Al35 h owever, exhibited limited ductility, commensurate with strong solution strengthening effects and only a partially developed intergranular fi lm. (C) 1997 Acta Metallurgica Inc.