Deformation characteristics of the intermetallic alloy 60NiTi |
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| Affiliation: | 1. NASA Glenn Research Center, Materials and Structures Division, Cleveland, OH 44135, USA;2. University of Toledo, Toledo, OH 43606, USA;3. Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;4. Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1 D-21502, Geesthacht, Germany;1. Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road 27, Cambridge CB3 0FS, UK;2. Institute of Materials Science and Technology, Vienna University of Technology, Favoritenstraße 9-11, Vienna 1040, Austria;3. Christian Doppler Laboratory “Early Stages of Precipitation”, Vienna University of Technology, Favoritenstraße 9-11, Vienna 1040, Austria;4. National Institute for Research and Development in Electrical Engineering INCDIE ICPE-CA, Advanced Materials Department, Splaiul Unirii, nr. 313, Sector 3, Bucharest, Romania;1. Department of Mechanical and Industrial Engineering, University of Toronto, Canada;2. Ontario Centre for the Characterisation of Advanced Materials, Dept. of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada;3. Univ. Bourgogne Franche-Comté FEMTO-ST Institute CNRS/UFC/ENSMM/UTBM, Department of Applied Mechanics, 24 rue de l′Epitaphe, F-25000 Besançon, France;1. College of Manufacturing Science and Engineering, Sichuan University, Chengdu, Sichuan 610065, PR China;2. Institute of Machinery Manufacturing Technology, Chinese Academy of Engineering Physics, Mianyang, Sichuan 621900, PR China |
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| Abstract: | The deformation behavior of a Ni-rich Ni55Ti45 (at.%) alloy, commonly known as 60NiTi (as designated in wt.%), was analyzed using neutron and synchrotron x-ray diffraction during in situ isothermal tension and compression loading, and pre and post-test electron microscopy. The alloy was shown to exhibit remarkable strength and high hardness resulting from a high density of fine Ni4Ti3 precipitates (size ∼67 nm), which were uniformly dispersed throughout the matrix after a solution treatment and oil quench. The precipitate volume fraction was 55 ± 3%, determined from both the neutron Rietveld refinement and conventional x-ray measurements. Non-linear stress-strain behavior was observed in tension (but not in compression) and was attributed to reversible stress-induced martensite (SIM) that forms to accommodate the stress as revealed by neutron diffraction measurements. The tensile and compressive neutron data also showed peak broadening and residual lattice strains. Transmission and scanning electron microscopy revealed stress-induced coarsening of Ni4Ti3 precipitates in both tension and compression tested samples, but precipitation and growth of the stable Ni3Ti phase was observed only after tensile testing. Finally, the potential ramifications of these microstructural changes are discussed. |
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| Keywords: | 60NiTi Shape memory alloy Stress-induced martensite Strain-induced coarsening Bearing |
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