THE ALPHA/BETA-HYDROGEN MISCIBILITY GAPS IN HYDROGENATED PD-Y-IN(SN, PB) TERNARY ALLOYS

The lattice parameters and hardness of Pd-Y-In(Sn, Pb) ternary alloys and the critical composition for the disappearance of the (alpha+beta) hydrogen miscibility gap at room temperature in hydrogenated alloys were examined as a preliminary study for use as possible diffusion membranes for hydrogen purification. All alloys of Pd100-x-yYx(In(Sn, Pb))y with x up to 6.0 at.% Y, and with y up to 10.0 at.% In and 9.0 at.% Sn(Pb) consist of a single alpha-Pd phase. The lattice parameters of the alloys with a given content of In, Sn and Pb increase with increasing Y content, and at the same Y content they increase with increasing In, Sn and Pb contents. The lattice expansion for the Pd-Y-Pb alloy system is larger than for the other alloy systems Pd-Y-In and Pd-Y-Sn. The hardnesses of the alloys increase with an increase of the lattice expansion, and at the same hardness values the lattice expansion of the Pd-Y-Pb system is larger than that of the other systems. The extension of the (alpha+beta) miscibility gap in the Pd-Y-In(Sn, Pb)-H systems decreases with an increase of In, Sn and Pb content.