Atomic Rearrangement and Phase Transformation during Aging at 480 °C in a Maraging-300 Steel

Maraging steels are known to achieve the best mechanical properties when aged around 480 °C. However, the precipitate formation process is still not straightforward enough at this temperature. In this research, Mössbauer spectroscopy, complemented with transmission electron microscopy, x-ray diffraction, hardness measurements, and optical microscopy techniques, was used to investigate the phase transformation process of solution-treated and 480 °C-aged Maraging-300 steel specimens. The results indicated that the precipitation of intermetallic compounds starts at the early stages of aging and that these precipitates are Fe-free, which are responsible for improving mechanical properties. Atomic mobility is discussed, and precipitate formation is evidenced. Small amounts of reverted austenite due to precipitate dissolution were detected at longer aging times, and the formation of paramagnetic iron-rich phases is also suggested.