On the remarkable thermal stability of nanostructured ferritic alloys

We explore the high-temperature thermal stability of a class of potentially transformational materials for high temperature applications that we call nanostructured ferritic alloys (NFAs). NFAs manifest unprecedented properties including outstanding strength and irradiation tolerance that are primarily enabled by an ultrahigh concentration of Y–Ti–O nanoscale features (NFs). One significant challenge is to understand and control the stability of the NFs under extreme high temperature and long-time aging conditions. Thermal aging was carried out between 800 °C and 1000 °C for times up to 32.4 kh. A toolkit of characterization techniques shows that the NFAs and NFs are stable below 900 °C, while experiencing slow, but systematic coarsening at 950 °C and especially 1000 °C, accompanied by small reductions in strength. Other microstructural changes are also described.