Radiation damage can lead to significant property changes in structural materials. Radiation induced swelling, embrittlement or increase in yield strength are just a few. The dose, dose rate and temperature together determine the effect on the material which can have significant engineering impact. Therefore, it is key to understand how a material changes under radiation and being able to predict the property changes. Small scale mechanical testing offers a wide range of benefits especially when working with materials in nuclear application. The reduced size allows to handle highly radioactive materials while also enabling ion beam irradiations as a surrogate to quantify radiation damage. In this work we will provide examples on how small-scale mechanical testing provided deep insight into the mechanical deformation of materials after irradiation. We investigate how the properties change due the radiation induced dissolution of precipitates or due to the formation of new features such a cavities, dislocation loops or precipitates. We will highlight how the plasticity and associated mechanical property values change. Last but not least we will introduce scaling studies performed in order to extract bulk properties from small scale tests. Mesoscale mechanical tests enabled using laser fabrications are shown.
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Themes: Mechanical Behavior in Nuclear Materials
HIGH TEMPERATURE CREEP CAVITATION IMAGING AND ANALYSIS IN 9%CR 1%MO P91 STEELS
The creep lives of enhanced high-temperature strength and creep resistance of 9%Cr 1%Mo P91 steels in boiler and piping systems of high-temperature plants are limited by the formation of cavitation. P91 steels are characterised by various secondary phases and a complex grain boundary microstructure which leads to regions of increased stress accumulation resulting in the initiation of cavities. In order to predict and possibly extend the creep lives of P91 structure components in energy applications, it is important that the processes promoting the initiation and early growth of cavities are understood. This paper employs microscopy techniques as well as image segmentation tools in order to quantify and characterize the cavitation and the secondary phases present in ex-service and creep tested P91 samples.
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