Liquid phase separation, solidification and phase transformations of Gd–Ti and Gd–Ti–Al–Cu alloys

Phase equilibria of the quaternary Gd–Ti–Al–Cu system have been studied with particular respect to solidification and phase separation phenomena in metallic glasses. Along the section Gd55−xTixAl25Cu20 the primary solidifying phase changes from Gd2CuAl (x=0) toward α-Ti (x≥10) with rising Ti-fraction x. This is accompanied by an upturn of the liquidus temperature from TL=745 °C to TL>1100 °C. The miscibility gap predicted from thermodynamic calculations for Gd55−xTixAl25Cu20 melts at intermediate Ti-fractions was not verified experimentally. Unlike binary Gd–Ti melts, levitated Gd–Ti–Al–Cu droplets do not exhibit liquid phase separation features after quenching from different holding temperatures, even at high melt undercooling up to 200 K prior to solidification.