TG3: Small Angle Neutron Scattering in support of NeT

 

Small angle neutron scattering (SANS) facilitates the study of material heterogeneities by analyzing the scattering patterns of neutrons after passing through the specimen under investigation. Such analysis can give information about the size, shape and distribution of heterogeneities such as voids and precipitates. TG3 employs SANS to investigate the effects of high temperatures on the microstructure of materials relevant to the work in NeT.

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The first investigations were undertaken simply in the context of TG3 on thermal ageing on cast duplex (austenitic-ferritic) stainless steels, which are used for some components of the primary loop of light water reactors. These steels are prone to thermal ageing at operating temperatures of around 300 °C due to microstructural evolution of the ferritic phase. The ageing effects were clearly demonstrated, albeit only for ageing temperatures of 350°C and higher as no long term aged specimens were available for lower temperatures.

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In the context of Task Group 4, SANS has been used to study phase separations and surface fractals of particles due to the welding process. Phase separations, did not seem to have fully taken place, nevertheless a small, but distinctive increase in the volume fraction of a chromium carbide phase in the fusion zone was derived from the data.

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In support of TG7, SANS measurements have been made around an electron beam weld and around a GMAW simulated repair weld in the aluminium alloy AA6061, which is a relevant alloy for research reactors. The first analyses suggest the formation of inclusions of varying sizes after welding.