Unusual thermal stability of nano-structured ferritic alloys

Abstract A scientific question vitally important to the materials community is whether there exist “self-assembled” nanoclusters that are thermodynamically stable at elevated temperatures. Using in situ neutron scattering, we have characterized the structure and thermal stability of a nano-structured ferritic alloy. Nanometer sized nanoclusters were found to persist up to ∼1400 °C, providing direct evidence of a thermodynamically stable alloying state for the nanoclusters. High-temperature neutron diffraction measurements show a stable ferritic matrix, with little evidence of recrystallization or grain growth at temperatures up to 1300 °C. This result suggests that thermally stable nanoclusters and the oxygen-vacancy interaction limit the diffusion of Fe atoms and hence the mobility of grain boundaries, stabilizing the microstructure of the ferritic matrix at high temperatures.