Investigation of the Thermodynamic Properties, Phase Relations, and Stability of the Cd–Gd System via Thermodynamic Remodeling

Abstract

The CAlculation of PHAse Diagram (CALPHAD) technique is used in the critical remodeling of the Cd–Gd system. On the basis of a new experiment in literature, the excess Gibbs energies of the solution phase expression (liquid, bcc, and hcp_A3) are described using the Redlich–Kister equation. Intermetallic compounds (α-Cd2Gd, β-Cd2Gd, and Cd45Gd11), which exhibit a homogeneity range, are treated as a two-sublattice model. Four compounds (Cd3Gd, Cd58Gd13, Cd6Gd, and Cd8Gd) are treated as stoichiometric compounds. Two Calphad-type thermodynamic descriptions are developed for the CdGd and bcc. Model I is to model the compound CdGd and bcc-Gd separately. Model II is to use the formula (Cd,Gd)0.5(Cd,Gd)0.5(Va)3 to describe the compound CdGd with a CsCl-type structure (B2) and cope with the disorder–order transition from bcc-A2 to bcc-B2. The present work displays that two eutectic reactions, five peritectic reactions, one peritectoid reaction, one eutectoid reaction, one polymorphic transformation, and one congruent reaction are observed in the Cd–Gd system.