Theoretical studies of Ir5Th and Ir5Ce nanoscale precipitates in Ir |
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Authors: | James R Morris Frank W Averill Valentino R Cooper |
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Institution: | 1. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA;2. Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996-0750, USAmorrisj@ornl.gov;4. Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996-0750, USA |
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Abstract: | Experimentally, it is known that very small amounts of thorium and/or cerium added to iridium metal form a precipitate, Ir5Th/Ir5Ce, which improves the high-temperature mechanical properties of the resulting alloys. We demonstrate that there are low-energy configurations for nanoscale precipitates of these phases in Ir, and that these coherent arrangements may assist in producing improved mechanical properties. One precipitate/matrix orientation gives a particularly low interfacial energy, and a low lattice misfit. Nanolayer precipitates with this orientation are found to be likely to form with little driving force to coarsen. The predicted morphology of the precipitates and their orientation with the matrix phase provide a potential experiment that could be used to test these predictions. |
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Keywords: | iridium interface structure first-principles calculations grain boundary segregation nanostructures |
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