Atom Probe Studies of the Fe–Cr System and Stainless Steels Aged at Intermediate Temperature: A Review

The α–α′ spinodal decomposition is known to occurr in iron–chromium-based model and industrial alloys during long-term aging at intermediate temperatures. This decomposition can be characterized unambiguously by atom probe, and its evolution quantified by means of various microstructural paramaters directly accessible from concentration profiles. Comparison with the existing theories of spinodal decomposition will be briefly examined. This decomposition has a direct influence on the material, and can be used to improve magnetic or mechanical properties. Conversely, some mechanical properties, such as impact toughness, are greatly degradated by this evolution, and can lead to serious problems when, for example, the integrity of large industrial components is affected. For this reason, extensive work has been carried out to understand the influence of the various alloying elements on the phase separation and on the embrittlement process. Atom probe contributions in this area will be presented in this paper.