Modeling phase separation and composition patterning in FeCrAl alloys at neutron irradiation

Abstract

Possible scenarios of the microstructural evolution of FeCrAl alloys under neutron irradiation are studied by using the phase-field method. The exploited approach is generalized by considering ballistic mixing of atoms, spatial rearrangement of point defects, and dynamics of their sinks (dislocation loops), self-consistently. Stability diagrams manifesting domains of main control parameters (irradiation temperature, damage rate, atomic relocation distance) governing precipitation are obtained. It is shown that depending on irradiation conditions a precipitation of the Cr-rich $\alpha'$-phase proceeds by either phase decomposition or composition patterning mechanism. 
Statistical analysis of precipitation kinetics is provided by studying precipitate number density, mean precipitate size and Chromium content in $\alpha'$-phase for a model alloy Fe-30\%-Cr-5\%Al. A locality of point defects distribution with high concentration and dislocation loops growth are discussed. The hardening change is estimated for two possible scenarios of precipitation. Obtained results are verified with experimental observations. This study provides a deep insight into details of microstructural transformation in FeCrAl alloys during neutron irradiation.