The controlling creep processes in TiAl alloys at low and high stresses |
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| Affiliation: | 1. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, PR China;2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PR China;3. Panzhihua University, Panzhihua 617000, PR China;1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi''an, Shaanxi, 710072, China;2. Chongqing Innovation Center, Northwestern Polytechnical University, Chongqing, 401135, China;3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China;1. CNRS, CEMES (Centre d’Elaboration de Matériaux et d’Etudes Structurales), BP 94347, 29 rue J. Marvig, F-31055 Toulouse, France;2. Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben, Austria |
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| Abstract: | The creep response of a nearly-lamellar Ti–47Al–4(W, Nb, B) alloy is studied at 760 °C in a wide stress range 100–500 MPa. The alloy exhibits excellent creep resistance with a minimum creep rate of 1.2×10−10/s at 100 MPa and the time to 0.5% creep strain of 1132 h at 140 MPa. The controlling creep process is probed by analysis of the post-creep dislocation structure and by observation of incubation period during stress reduction test. The results indicate that creep is controlled by dislocation climb at low stresses (Class II type) and by jog-dragged dislocation glide at high stresses (Class I type). The transition from Class II to Class I type creep occurs at about 180 MPa. The excellent creep resistance of the studied alloy compared to other W containing TiAl alloys is attributed to its highly stable lamellar microstructure consisting eventually of coarse gamma laths. |
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