[SY-B8] Constrained thermodynamic model for multi-component alloys under irradiation: A matrix formulation from first-principles Hamiltonian
Understanding the behaviour of multi-component alloys under irradiation is one of the great challenges for the development of materials for nuclear applications. Recent experimental investigations revealed that micro-structural evolution of multi-component metallic alloys formed by transmulation under neutron irradiation can be very complicated since they may undergo spinodal decomposition and radiation-induced precipitation due to the strong coupling between defects and local chemical environment. Very recently, it was shown that concentrated solute solution alloys including high-entropy alloys (HEAs) may exhibit significantly improved performance under irradiation that depends strongly on the number of alloying elements and local alloy composition.
In this work, a revisited constrained thermodynamic model, initially proposed by Georges Martin, has been developed to model multi-component alloys under irradiation. The model is based on ab initio calculations in combination with a cluster-expansion Hamiltonian generalized for systems containing vacancy (V) and interstitial (I) defects. It is found that this formalism can be mathematically represented in terms of a matrix formulation for any N-component system via cluster correlation functions, which in turn can be deduced consistently from Monte-Carlo simulations. Analytical expressions for local short-range order parameters for alloy components and configurational entropies as functions of temperature and composition have been derived explicitly from this matrix representation. In the first nearest-neighbour approximation, the new approach reproduces the ABVI Ising model for a binary system as well as the thermodynamic limit of the Cluster Variation Method. We apply this formalism to anomalous precipitation in W(Re,Os,Ta) alloys under neutron irradiation as well as in low activation bcc and high-radiation resistance fcc HEAs and their derivatives.
In this work, a revisited constrained thermodynamic model, initially proposed by Georges Martin, has been developed to model multi-component alloys under irradiation. The model is based on ab initio calculations in combination with a cluster-expansion Hamiltonian generalized for systems containing vacancy (V) and interstitial (I) defects. It is found that this formalism can be mathematically represented in terms of a matrix formulation for any N-component system via cluster correlation functions, which in turn can be deduced consistently from Monte-Carlo simulations. Analytical expressions for local short-range order parameters for alloy components and configurational entropies as functions of temperature and composition have been derived explicitly from this matrix representation. In the first nearest-neighbour approximation, the new approach reproduces the ABVI Ising model for a binary system as well as the thermodynamic limit of the Cluster Variation Method. We apply this formalism to anomalous precipitation in W(Re,Os,Ta) alloys under neutron irradiation as well as in low activation bcc and high-radiation resistance fcc HEAs and their derivatives.