Thermodynamic reassessment of Au-Pt-Sn system

Au-Pt-Sn alloys are a novel class of materials with promising catalytic properties. This study provides updated information on phase equilibrium structures and thermodynamics of the Au-Pt-Sn ternary system. The formation enthalpies of Au-Sn and Pt-Sn binary subsystems were predicted by first principles calculations and these values were further refined by CALPHAD method. The results obtained accurately reproduced the experimental data. The reassessed phase diagram of the Au-Pt-Sn ternary system accurately described the phase composition of several Au-Pt-Sn alloys, which is essential for further modifications of these materials.

Thermodynamic Modeling of the Al–Co–Pd Ternary System, Aluminum Rich Corner

The aluminum-rich corner of the Al–Co–Pd ternary system was thermodynamically modeled by the CALPHAD method in the present study. The ternary system is a complex system with many ternary phases (W, V, F, U, Y2, C2). All ternary phases, except phase U, were modeled as stoichiometric compounds. The order–disorder model was used to describe the BCC–B2 and BCC-A2 phases. Solubility of the third element in binary intermetallic phases (Al5Co2, Al3Co, Al9Co2, Al13Co4, Al3Pd and Al3Pd2) was modeled. The experimental results collected from the literature were used in the optimization of the thermodynamic parameters. A good agreement between the experimental results and the calculations was achieved.

Prediction of Cracking Susceptibility of Commercial Aluminum Alloys during Solidification

Cracking during solidification is a complex phenomenon which has been investigated from various angles for decades using both experimental and theoretical methods. In this paper, cracking susceptibility was investigated by a simulation method for three series of aluminum alloys: AA2xxx, AA6xxx, and AA7xxx alloys. The simulation tool was developed using the CALPHAD method and is readily applicable to multicomponent alloy systems. For each series of alloys, cracking susceptible index values were calculated for more than 1000 alloy compositions by high-throughput calculation. Cracking susceptible maps were then constructed for these three series of aluminum alloys using the simulated results. The effects of major and minor alloying elements were clearly demonstrated by these index maps. The cooling rate effect was also studied, and it was concluded that back diffusion in the solid can significantly improve the cracking susceptibility.

Phase Diagram of Binary Alloy Nanoparticles under High Pressure

CALPHAD (CALculation of PHAse Diagram) is a useful tool to construct phase diagrams of various materials under different thermodynamic conditions. Researchers have extended the use of the CALPHAD method to nanophase diagrams and pressure phase diagrams. In this study, the phase diagram of an arbitrary A–B nanoparticle system under pressure was investigated. The effects of the interaction parameter and excess volume were investigated with increasing pressure. The eutectic temperature was found to decrease in most cases, except when the interaction parameter in the liquid was zero and that in the solid was positive, while the excess volume parameter of the liquid was positive. Under these conditions, the eutectic temperature increased with increasing pressure.

Simulation of Fe-Ti-Sb Thernary Phase Diagram at Temperatures above 900 K

Heusler alloys have been considered as one of the most promising thermoelectric materials for electrical power generation in a temperature range of 500–800 °C. Establishment of phase diagrams allows one to predict formation, equilibria, and stability of phases in of these ternary alloys. In this work we report on the simulation and investigation of phase diagram and phase equilibria in ternary Ti-Fe-Sb system which is of considerable interest for thermoelectric applications. The simulation was carried out using the CALPHAD method in Pandat software. The existence of the thermoelectric Heusler TiFe1.5Sb phase was revealed in a temperature range from 970 to 1070 K. The equilibria between TiFe1.5Sb and other phases were determined. The entropy of formation was calculated for the phases existing at 970, 1020 and 1070 K using a fitting approach. A narrow equilibrium region containing pure body centered cubic Fe and TiFe1.5Sb was found.

Phase transformations and thermal conductivity of the In-Ag alloys

Phase transformations and thermal conductivity of three In-Ag alloys with 5, 15, and 45 wt.% of Ag were experimentally investigated in the present work. Phase transition temperatures were measured using differential scanning calorimetry (DSC). DSC heating scans were compared with the equilibrium and non-equilibrium solidification paths, calculated by using optimized thermodynamic parameters from literature and calculation of phase diagrams (CALPHAD) method. The flash method was employed for the determination of thermal diffusivity and thermal conductivity of the investigated alloys in the temperature range from 25 to 100 °C. It has been found that an increase in silver content does not lead to an increase in the thermal conductivity of the investigated alloys. Thermal conductivities for all three investigated In-Ag alloys slightly decrease with temperature increasing.