Order-disorder transitions of the Pd 7Dy(Y) phase in Pd-Dy(Y) alloys

Abstract

Electron diffraction and electrical resistance measurements of Pd-Dy(Y) alloys in the composition range between 8.0 and 17.5 at.% Dy(Y) indicate the presence of an ordered phase in the form of a Pd 7Dy(Y) superlattice. This is similar to the order found in Pd 7Ce and Pd 7Gd, which is isomorphous with Pt 7Cu. The order-disorder transition of the Pd 7Dy(Y) phase in the alloys between about 10.5 at.% Dy(Y) and the palladium-rich L1 2-type Pd 3Dy(Y) is accompanied with a peritectoid reaction: α- Pd + L1 2-type Pd 3Dy(Y)⇄Pd 7Dy(Y). The peritectoid temperature ( T c ) is equal to 767 ± 10 K for Pd 7Dy, and 777 ± 10 K for Pd 7Y. The order-disorder transition temperatures for the Pd-8.0at.%Dy(Y) and Pd-10.0at.%Dy(Y) alloys are lower than the peritectoid temperature and the transition temperatures correspond to the solid solubility limit of Dy(Y) in the α-Pd solid solution. The palladium-rich portion of the phase diagram of the Pd-Dy(Y) alloys associated with these new ordered Pd 7Dy(Y) phases is presented.