Fundamental mechanisms of removal of stacking fault tetrahedra by mobile low energy boundaries

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TECHNICAL SUMMARY: The objective of this work is to understand the fundamental mechanisms through which mobile twin boundaries (TBs) actively engage and rapidly remove stacking fault tetrahedra (SFTs). The ultimate goal is to design advanced metallic materials that can effectively remove SFTs at low-to-intermediate temperatures. SFTs are detrimental defects in neutron or proton irradiated structural metallic materials with face-centered-cubic structures as they can induce significant hardening and swelling. The PI will use a combination of in situ radiation and in situ nanoindentation technique to investigate the interaction of SFTs with TBs. These studies can explain the annihilation of SFTs by TBs and provide crucial information to validate annihilation mechanisms predicted by MD simulations. Also significant mobility of TBs may make them attractive candidates to remove radiation induced immobile defects, such as SFTs. NON-TECHNICAL SUMMARY:If successful, the benefits of this research will include discovery of important criteria for the design of swelling resistant structural materials for next generation nuclear reactors, and offer the basis for further exploration of physics of radiation induced twin boundary migrations. This project will provide research training to graduate and undergraduate students at Texas A&M University (TAMU). Special effort will be made to recruit female and other minority students through the "Pathway to Ph.D program" funded by TAMU. The project will also enhance the materials science and nanoengineering curricula by incorporating relevant results into classes when introducing advanced nanomaterials, and benefit the new formed Department of Materials Science and Engineering. The PI will disseminate results to a much broader audience by involving high school teachers in the research project through NSF-RET program, and attending international conferences. Collaborations with McMaster University and several DOE National Laboratories will offer graduate students summer research experience.