Coarsening of ordered intermetallic precipitates with coherency stress |
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| Affiliation: | 1. Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208, USA;1. Mechanical and Civil Engineering Department, Florida Institute of Technology, Melbourne, Florida, 32901, USA;2. School of Data and Computer Science, Sun Yat-Sen University, Guangzhou, 510006, P. R. China;3. Department of Materials Science and Engineering, 100 Rhines Hall, Gainesville, FL 32611-6400, USA;4. Emeritus, Florida Institute of Technology, Melbourne, FL, 32901, USA;1. University of Chinese Academy of Sciences, Beijing 100049, China;2. Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;1. Beijing Advanced Innovation Center for Material Genome Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083, China;2. Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany |
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| Abstract: | The morphological evolution and coarsening kinetics of ordered intermetallic precipitates with coherency stress were studied using a diffuse-interface phase-field model in two dimensions (2D). The emphasis is on the effects of precipitate volume fraction. The average aspect ratio of the precipitates in the microstructure is found to increase with time and decrease with volume fraction. Contrary to all the existing coarsening theories but consistent with a number of experimental measurements on the coarsening kinetics of ordered γ′ precipitates in Ni-base superalloys, we found that the coarsening rate constant from the cubic growth law decreases as a function of volume fraction for small volume fractions (≲20%) and is constant for intermediate volume fractions (20–50%). From the simulation results, we infer that the two length scales in a stress-dominated coherent two-phase microstructure, the average precipitate size and average spacing between arrays of aligned precipitates, follow different growth exponents. It is demonstrated that as the volume fraction increases, the precipitate size distributions become broader and their skewness become increasingly positive. |
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