The thermodynamic database for the Al-Fe-Mg-Mn-Si system is developed based on the constituent binary, ternary, and quarternary systems. The computed phase diagrams agree well with the experimental data. The obtained database is used to describe the solidification behavior of Al 356.1 (91.95Al-0.46Fe-0.3Mg-0.32Mn-6.97Si, in wt.%) and Al 356.2 (92.77Al-0.08Fe-0.35Mg-6.8Si, in wt.%) under equilibrium and Gulliver-Scheil non-equilibrium conditions. The reliability of the established thermodynamic database is also verified by the good agreement between calculation and experiment for both equilibrium and Gulliver-Scheil non-equilibrium solidifications. Microstructure and microsegregation of the directionally solidified Al 356.1 alloy are investigated with a growth rate of 0.04445 cm s-1 and a temperature gradient of 45K cm-1. Fractions of solids formed are measured by using quantitative image analysis of back-scattered electron, and solute redistribution in the primary (Al) is determined by means of an area scan approach with a total of 2400 electron probe microanalysis point counts. A micromodel, which includes solid-state diffusion, secondary dendrite arm coarsening, and dendrite tip and eutectic undercooling, is coupled with a multicomponent phase diagram calculation engine (PanEngine) to predict the microstructure and microsegregation of the solidified alloy. Quantitative agreement of the model prediction with the experiment is obtained for concentration distributions in the primary (Al), the types and amounts of phases formed, and the solidification path.

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 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.

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

The modified cluster-site approximation (CSA) model has been used to model the f.c.c. phases (ordered L12 and disordered A1) in the Ni-Al system. The CSA model has the advantage over the cluster variation method (CVM) in that the independent variables in the free energy functional are the site probabilities and not the cluster probabilities. Unlike the zeroth approximation, however, the CSA takes short-range order into consideration, an essential requirement for describing phases that undergo an order/disorder transition, as does the f.c.c. phase in the Ni-Al system. By using the modified CSA model, we have been able to obtain an improved phenomenological description of this system with the use of fewer model parameters than used in previous descriptions. The topology of the calculated metastable f.c.c. phase diagram is similar to the one obtained using a 'first-principles'-CVM approach, whereas the f.c.c. phase diagrams based on the previous phenomenological descriptions are unsatisfactory.