Small-angle neutron scattering uncovers irradiation effects on Fe-Cr model alloys and a steel

What is it about?

Structural and magnetic inhomogeneities of a few nanometre in size scatter incident neutrons by small angles. The measured intensities of scattered neutrons can be translated into type and number density of such nanofeatures formed in Fe-Cr alloys as a result of irradiation. Our measurements essentially confirm the types of irradiation-induced nanofeatures expected on the basis of the Fe-Cr phase diagram and previous studies. Major characteristics such as size and number density have been estimated as function of chromium content, irradiation dose and irradiation temperature. It might be surprising at first glance that the 9% Cr steel known as Eurofer97 is even more resistant to neutron irradiation than the purer Fe-9Cr model alloy. The reason is the high density of point defect sinks such as grain boundaries available in the steel by design.

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Photo by Shavonne Yu on Unsplash

Photo by Shavonne Yu on Unsplash

Why is it important?

Atomistic modelling of the microstructure evolution in steels exposed to neutron irradiation is still in its infancy because of the complexity of the processes. Modell alloys and modelling-oriented experiments allow dedicated models to be validated and the understanding of influence factors to be improved. In this respect, application of magnetic small-angle neutron scattering contributed to the generation of basic information and quantitative characteristics of irradiation-induced nanofeatures. Corresponding data, trends and correlations with mechanical properties observed for the ferritic-martensitic steel Eurofer97 are particularly relevant as this steel is a candidate for future applications in fusion energy devices.

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