Atomic scale analysis and phase separation understanding in a thermally aged Fe–20 at.%Cr alloy

Fe–Cr model alloys are of interest for understanding of phase separation in structural material for fusion or fission reactors. This motivated the quantitative study of the phase separation in a thermally aged (773 K) Fe–20 at.%Cr alloy using a Tomographic Atom Probe. It is shown that the chromium content in the α′ phase evolves with ageing time synonymous of a non-classical nucleation mechanism. The overlap of the nucleation and coarsening regimes is observed. A non-steady coarsening regime occurs before 1067 h of ageing. The solubility limit at 773 K is found to be 14 at.%. A maximum concentration of (83 ± 1) at.% is observed for the Cr-concentration in α′ precipitates.