Experimental and Theoretical Background of Multi-component Cluster Formation in Reactor Pressure Vessel Steels due to Neutron Irradiation

Sophisticated microstructural analysis methods like small angle neutron scattering and atom probe field ion microscopy have proven the presence of so-called multicomponent clusters due to neutron irradiation in ferritic reactor pressure vessel steels. The formation of such clusters is surprising from the thermodynamic point of view. The cluster formation from the solid solution was modelled as phase transformation of the first kind that corresponds to the negative minimum of the so-called thermodynamic force under consideration of six components. The essential parameter is the sum of interaction energy between all pairs of atoms in the system. The approach result in stable multicomponent cluster if the clusters exhibit a high content of vacancies and a core-shell structure with very high vacancy content within the shell. The kinetics background of the suggested model was investigated using the cluster dynamic approach generalized for multiple components. The computed results are consistent with the experimental findings.