Computational Thermodynamics of Mo-Ti-Si-C system to develop new short Ceramic fiber reinforced-Intermetallic Matrix Composites
DAUFRESNE E. 1,2, BECHELANY M. 1, LE PETITCORPS Y. 1, DEZELLUS O. 2
1 ThermoStructural Composites Laboratory, UMR 5801, Safran, CEA, CNRS, Université de Bordeaux, 3 Allée de la Boétie, 33600 Pessac, FRANCE , Bordeaux, France; 2 Multi-Materials and Interfaces Laboratory, UMR 5615, CNRS, Université Claude Bernard Lyon 1, 6 rue Victor Grignard, FRANCE, Lyon, France
Owing to their superior damage tolerance compared to monolithic intermetallic as well as their great production versatility, discontinuous ceramic fiber reinforced-Intermetallic Matrix Composites (IMC) are currently being investigated to form complex-shape materials for aerospace propulsion applications. Among them, discontinuous SiC reinforced-Mo-Ti-Si composites are particularly promising for their outstanding high-temperature oxidation resistance [1].
Improvements of the latter especially implies increasing its overall toughness and high-temperature creep resistance and can be achieved through the development of a homogeneous multi-component intermetallic matrix. To ensure an adequate SiC-fibers preservation, which deterioration could weaken the composite’s comprehensive mechanical properties, a thermodynamic study of their compatibility with the matrix appears to be critical. An Integrated Computational Materials Engineering (ICME) approach named CALPHAD (CALculation of PHAse Diagram) based on the phases’ Gibbs free energy function minimization has therefore been considered for the quaternary Mo-Ti-Si-C system [2].
As there was no exhaustive reliable thermodynamic database involving the four atoms of interest to predict accurate phase equilibria in the existing literature, a custom one has been created by merging previously assessed binary and ternary sub-systems. Available experimental and ab-initio data, in particular on Mo-Ti-Si solid solutions, were collected through extensive literature research and added by interpolation. Phases’ free energies were then optimized using the least-square algorithm and extrapolated to model the Mo-Ti-Si-C system. Finally, the thermodynamic calculations carried out allowed a better understanding of the effect of temperature on the matrix/reinforcement reactivity as well as a first screening of satisfactory Mo-Ti-Si-C matrix compositions chemically stable with the SiC reinforcement.
Previously synthesized Mo-Ti-Si-C-matrixes reinforced with discontinuous SiC fibers using Spark Plasma Sintering were compared to computed solid compositions and simulated phase equilibria.
References
[1] C. Ward-Close, R. Minor and P. Doorbar, Intermetallics, 1996, 4, 217-229
[2] A. Luo, Calphad, 2015, 50, 6-22
