Anomalous small-angle X-ray scattering from a maraging alloy during martensite unmixing

Abstract
The unmixing of a quaternary Fe-Ni-Co-Mo maraging alloy has been studied by anomalous small-angle X-ray scattering performed at the FeK absorption edge only, transmission electron microscopy and Mössbauer spectrometry. For suitable unmixing temperatures and times it was found that the lath martensite decomposes into two phases: isothermal ω-phase precipitates enriched in solute elements, and a matrix depleted in solute elements. The ω-phase does not contain iron and, for a given unmixing temperature, its composition is fairly constant as a function of the ageing time. For the lower ageing temperature (438°C) the atomic ratio C Mo/C Ni+Co is close to that of the A2B type structure (0·50), but seems to increase slightly when the temperature is increased to 458°C.