Producing fully-lamellar microstructure for wrought beta-gamma TiAl alloys without single α-phase field |
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| Affiliation: | 1. Advanced Materials Research Center (AMRC), Northwest Institute for Nonferrous Metal Research, Xi''an 710016, China;2. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;1. State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China;2. Department of Mechanical Engineering, School of Machinery and Automation, Wuhan University of Science and Technology, Wuhan 430081, China;1. Centre for Advanced Structural Materials, Department of Mechanical and Biomechanical Engineering, College of Science and Engineering, City University of Hong Kong, Hong Kong, China;2. Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, China;3. Herbert Gleiter Institute For Nanoscience, Nanjing University of Science and Technology, Nanjing, China;1. Chair of Physical Metallurgy and Materials Technology, Brandenburg University of Technology Cottbus, Konrad-Wachsmann-Allee 17, Cottbus D-03046, Germany;2. Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Max-Planck-Str. 1, Geesthacht D-21502, Germany;3. GfE Fremat GmbH, Lessingstr. 41, Freiberg D-09599, Germany;4. Rolls-Royce Deutschland Ltd & Co KG, Eschenweg 11, Blankenfelde-Mahlow D-15827, Germany |
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| Abstract: | Fine-grained fully-lamellar (FL) microstructure is desired for TiAl components to serve as compressor/turbine blades and turbocharger turbine wheels. This study deals with the process and phase transformation to produce FL microstructure for Mo stabilized beta-gamma TiAl alloys without single α-phase field. Unlike the α + γ two-phased TiAl or beta-gamma TiAl with single α-phase field, the wrought multi-phase TiAl–4/6Nb–2Mo–B/Y alloys exhibit special annealing process to obtain FL microstructure. Short-term annealing at temperatures slightly above β-transus is recommended to produce the desired FL microstructure. The related mechanism is to guarantee the sufficient diffusion homogenization of β stabilizers during single β-phase annealing, and further avoid α decomposition by α → γ + β when cooling through α + β + γ phase field. The colony boundary β phase contributes to fine-grained nearly FL microstructure, by retarding the coarsening of the α phase grains. |
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| Keywords: | A Titanium aluminides based on TiAl B Phase transformation C Heat treatment D Microstructure |
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