The phase equilibria in Mg-rich corner of Mg-Ca-Gd and Mg-Ca-Nd ternary systems at 400℃ were determined through the equilibrated alloy method by using XRD, SEM, EPMA and DSC. Partial isothermal sections in Mg-rich corner of Mg-Ca-Gd and Mg-Ca-Nd ternary systems at 400 ℃ were constructed from 13 alloys. A three-phase region of a-Mg, Mg41RE5 and Mg2Ca was determined in both ternary systems. It is formed by a similar ternary eutectic reaction L→a-Mg＋Mg2Ca＋Mg41RE5 at 499.6 ℃ and 505.6 ℃, respectively. It is found that the maximum solubility of Ca in Mg5Gd is 3.68% （molar fraction） and 3% of Gd can be dissolved in Mg2Ca in the Mg-Ca-Gd system at 400 ℃. While in the Mg-Ca-Nd system, the maximum solubility of Ca in Mg41Nd5 is 3.57% and 1.24% of Nd can be dissolved in Mg2Ca at 400 ℃. Other three-phase equilibria existing in Mg-rich corner of Mg-Ca-Gd system are a-Mg＋MgsGd＋T and MgsGd＋Mg2Ca＋T and the three-phase equilibrium in Mg-rich corner of Mg-Ca-Nd system is Mg3Nd＋Mg2Ca＋ Mg41Nd5.
The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.
