Highlights

Ion Irradiation-Induced Microstructure Evolution of a Fe-12Cr-0.1C Model Martensitic Steel Studied In Situ in a TEM

Scientific Achievement

Two model martensitic steels of composition (wt%) Fe-12Cr-0.1C and Fe-9Cr-0.1C were irradiated with 1 MeV Kr ions at 25°C, 200°C, 300°C, 400°C, and 500°C to doses up to 6 dpa in situ in the IVEM.  The microstructure evolution under irradiation was followed and characterized at successive doses in terms of irradiation-induced defect formation and evolution, black dot density, nature and number density of defect clusters present, and stability of the as-fabricated microstructure (i.e. dislocation networks).

The overall goal of the irradiations is to perform a direct determination of the spatial correlation of the time evolution of the irradiation-induced defect structures with the pre-existing alloy microstructure including lath boundaries, network dislocations and carbides which is made possible by the IVEM facility where the sample can be examined in the microscope as the irradiation proceeds.

The effect of the irradiation temperature on the damage density and on the stability of the initial microstructure could be investigated thanks to the availability of heating stage in the IVEM.  The facility also allowed to separate possible the effects of temperature investigated from possible dose rate effects as the dose rate could be controlled by keeping the flux fixed.

Significance

The overall scope of the project (within framework of NERI-C, Gen-IV reactors)is to examine the microstructure development of F/M steels under irradiation at early stages of irradiation (low doses relative to the doses expected in Gen-IV type reactors) and be able to compare with computer simulations, thus validating these calculations so that they can be used to predict in reactor behavior.

This work provides a platform of results which computer simulations can be tested with.  The unique features of the IVEM (ability to characterize the defects in situ as they develop, study the interaction with the microstructure, follow specific locations etc) make it ideal to obtain this data.  Ultimately it will provide a validation for models based on rate theory and allow for prediction of structural materials response to irradiation.  This is a critical issue for selection of cladding and structural materials for the next generation of nuclear reactors.

This work is part of a DOE NERI Research consortium on Consortium on Cladding and Structural Materials for Advanced Reactor Systems in close collaboration with our partner institutions.

Performers

D. Kaoumi, A. T. Motta (Penn. State U.); M. Kirk (Argonne-MSD)