Building a database for the prediction of phases in Pt-based superalloys

Work is being done at Mintek and at Leeds University to build up a Pt-Al-Cr-Ru database for the prediction of phase diagrams for further alloy development by obtaining good thermodynamic descriptionptions of all of the possible phases in the system. The available databases do not cover all of the phases, and these had to be gleaned from literature or modelled using experimental data. Similarly, not all of the experimental data were known, and where there were gaps or inconsistencies, experiments had to be undertaken. A preliminary version of the database was constructed from assessed thermodynamic data-sets for the binary systems only. The binary descriptionptions were combined, allowing extrapolation into the ternary systems, and experimental phase equilibrium data were compared with calculated results. Very good agreement was obtained for the Pt-Al-Ru and Pt-Cr-Ru systems, which was encouraging and confirmed that the higher-order systems could be calculated from the binary systems with confidence. Since some of the phase models in earlier databases were different, these phases had to be remodelled. However, more work is ongoing to obtain information concerning the ternary phases present in the Al-Cr-Ru, Pt-Al-Ru (two ternary compounds in each) and Pt-Al-Cr (possibly more than three ternary compounds) systems. At a later stage of the research problems with the thermodynamic descriptionptions of the Cr-Ru and Pt-Cr binary systems were found. A programme of experimental work to overcome these has been devised, and is being undertaken. Parallel work at the University of Bayreuth, Germany, entails the creation of a Pt-Al-Cr-Ni database using a slightly different approach that utilizes more data from ab initio calculations and more complex models. The Cr-Pt binary phase diagram has been reassessed, and the latest results of thermodynamic modelling are presented. Keywords: Pt-based alloys, phase diagram calculations.