期刊
ACTA MATERIALIA
卷 61, 期 18, 页码 6830-6842出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2013.07.062
关键词
beta Ti alloy; Synchrotron X-ray diffraction; Stress-induced martensite transformation; Lattice strain
资金
- US Department of Energy, Office of Science [DE-ACO2-06CH11357]
- Office of Science
- Wayne Metals management is greatly appreciated
An in situ high-energy X-ray diffraction cyclic tension test was carried out on a beta III Ti alloy to study its micromechanical behavior and the stress-induced phase transformation. Pre-strained material showed a microscopic multi-stage re-loading behavior following the sequence of elastic deformation, stress-induced martensite (SIM) transformation, a second stage of elastic deformation followed by a final stage of SIM transformation. Based on the relationship of internal strains and diffraction intensities between the beta phase and the SIM, it is concluded that after a small strain deformation, the austenite is divided into two different sets of grains with different properties. Those that previously experienced phase transformation have a lower critical stress for the SIM transformation due to residual martensite and dislocations, while the rest have a higher trigger stress and only transform to martensite after the stress is back to levels comparable to where transformation was seen in the previous cycle. The different properties within the same austenite grain family cause the multistage re-loading behavior. The reverse phase transformation during unloading was impeded by the combination of increased dislocation density in the austenite and the increased tensile strain in the martensite prior to unloading. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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