The Nb-Ni system is reassessed on the basis of a critical literature review involving recent experimental data. These newly published experimental data include the phase relation associated with the NbNi8 phase, phase transition temperatures resulting from selected alloys, all invariant reaction temperatures, and enthalpies of mixing of liquid, as well as the crystallographic data on the μ(Nb7Ni6) phase. A consistent thermodynamic data set for the Nb-Ni system is obtained by optimization of the selected experimental values. The calculated phase diagram, crystallographic properties and thermodynamic properties agree reasonably with the experimental data. Noticeable improvements have been made, compared with the previous thermodynamic optimizations.

The phase equilibria of the Co-Cu-Ti system at 850℃ are investigated using a high-efficiency diffusion couple and six key ternary alloys. The samples are examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. At 850℃, no ternary compound is found. The Ti3Cu phase is a metastable phase. The solubilities of Cu in Ti2Co, TiCo, TiCo2 (c) and TiCo3 were determined to be 8.7, 36, 2 and 5.4, respectively. And the solubilities of Co in Ti2Cu, TiCu, Ti3Cu4, and TiCu2 were measured to be 6.6, 0.7, 2.4, and 10.2, respectively. The following 9 three-phase equilibria are observed: (Ti)+Ti2Co+Ti2Cu, Ti2Co+Ti2Cu+TiCo, Ti2Cu+TiCu+TiCo, TiCu+Ti3Cu4+TiCo, Ti3Cu4+TiCu2+TiCo, TiCu2+TiCo+(Cu), TiCo+TiCo2(c)+(Cu), TiCo2(h)+TiCo3+(Cu), and TiCo3+(Co)+(Cu).

The isothermal section at 950℃ of the Co-Nb-Ti system was investigated using diffusion couples and six ternary alloys. The specimens were examined by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. No ternary compound was found. Nine three-phase equilibria were observed. The binary intermediate phases NbCo3 and Nb2Co7, the existence of which is still controversial in the literature, were observed at 950℃. The solubilities of Ti in Nb2Co7, NbCo3, γ-NbCo2 and μ-Nb6Co7 were determined to be 1.9, 16.4, 14.4 and 17.4 at.%, respectively. The solubilities of Nb in TiCo3, TiCo2(h), TiCo2(c), TiCo and Ti2Co were determined to be about 5.7, 11.0, 2.6, 13.6 and 3.1 at.%, respectively.

A method to estimate the thermodynamic properties of ternary alloys from those of constitutive binary alloys was proposed. The thermodynamic data of binaries were calculated by Miedema's theory. The asymmetry of constitutive binary alloys in the ternary system was considered in the present extrapolating procedure. The dependence of asymmetric constituent on the choice in Toop's model was overcome. The present method was used to calculate the formation enthalpies of Fe-Ni-V alloys. The agreement between the calculation and experiment is reasonable. So the formation enthalpies of Fe-Al-RE (RE=lanthanide metal) ternary alloys were calculated with the present method. The relative stability of RE(Fe1-xAlx)13, RE2(Fe1-xAlx)17 and RE5(Fe1-xAlx)17 were also studied with the present method.

rature five groups of authors [1, 2, 4, 6, 7] reported an eutectic reaction type (L→(Al)+Al45Cr7), whereas the remaining two groups [3, 5] suggested a peritectic one, L+Al45Cr7→(Al). In the phase diagram assessed by Murray [11, 12], the peritectic reaction type is adopted. The purpose of the present work is to identify the degenerated nature for the invariant reaction among (Al), liquid, and Al45Cr7 by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) methods