High rate directional solidification and its application in single crystal superalloys |
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| Affiliation: | 1. State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering, Tianjin University, Tianjin, 300354, PR China;2. Beijing CISRI-GAONA Materials & Technology CO., LTD, PR China;3. High Temperature Materials Research Institute, Central Iron & Steel Research Institute, PR China;1. Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China;2. Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany;3. Advanced Photon Source, Argonne National Laboratory, Argonne IL60439, USA;4. Department of Mechanical Engineering, Tufts University, Medford MA02155, USA;1. State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China;2. School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China;3. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;1. Max-Planck-Institut für Eisenforschung GmbH, 40237, Düsseldorf, Germany;2. Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 6, 91058, Erlangen, Germany;3. Institute of General Materials Properties, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 1, 91058, Erlangen, Germany;4. Institut für Werkstoffe, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44 780, Bochum, Germany;1. Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, PR China;2. Foundry Institute, RWTH Aachen University, Aachen 52056, Germany;3. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, PR China |
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| Abstract: | In the present paper there are two parts contributing to the discussion of high rate directional solidification and its application. The first part aims to characterize the high rate directional solidification of various kinds of alloys. It was found that the relevant cooling rate of the high rate directional solidification is defined to be within 1–103 K/s (solidification rate is 10−4–10−1 m/s as GL=100 K/cm) and that it is located in the region between the near-equilibrium slow growth rate and the rapid solidification rate beyond the equilibrium condition, whilst at the same time there occurs a series of turning effects of interface stability and morphologies. With the increase in the growth velocity the interface with the plane front evolves to cells and dendrites at the stage of near-equilibrium and with a further increase in growth rate they transformed reversibly from dendrites to cell structure and then to the absolute stability of a planar interface. The change of solute segregation reveals the same from a low segregation, then increased and finally reduced again. An explanation based on effective constitutional supercooling about the evolution of interface morphologies with respect to the changes of growth rate is proposed.The second part is devoted to introducing experimental results for single crystal superalloys using the rate directional solidification principle. It is shown that the single crystal superalloys CMSX-2 and NASAIR 100 exhibit significant improvement in microstructure segregation and mechanical properties at high temperature both in the as-cast and after-heat-treatment conditions with the high rate directional solidification technique. |
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