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Li CW, Han LZ, Luo XM, Liu QD, Gu JF. Fine structure characterization of martensite/austenite constituent in low-carbon low-alloy steel by transmission electron forward scatter diffraction. J Microsc 2016; 264:252-258. [PMID: 27571433 DOI: 10.1111/jmi.12465] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 07/02/2016] [Accepted: 08/02/2016] [Indexed: 11/30/2022]
Abstract
Transmission electron forward scatter diffraction and other characterization techniques were used to investigate the fine structure and the variant relationship of the martensite/austenite (M/A) constituent of the granular bainite in low-carbon low-alloy steel. The results demonstrated that the M/A constituents were distributed in clusters throughout the bainitic ferrite. Lath martensite was the main component of the M/A constituent, where the relationship between the martensite variants was consistent with the Nishiyama-Wassermann orientation relationship and only three variants were found in the M/A constituent, suggesting that the variants had formed in the M/A constituent according to a specific mechanism. Furthermore, the Σ3 boundaries in the M/A constituent were much longer than their counterparts in the bainitic ferrite region. The results indicate that transmission electron forward scatter diffraction is an effective method of crystallographic analysis for nanolaths in M/A constituents.
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Affiliation(s)
- C W Li
- Institute of Materials Modification and Modeling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - L Z Han
- Institute of Materials Modification and Modeling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - X M Luo
- Institute of Materials Modification and Modeling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - Q D Liu
- Institute of Materials Modification and Modeling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - J F Gu
- Institute of Materials Modification and Modeling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China.
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Colla MS, Amin-Ahmadi B, Idrissi H, Malet L, Godet S, Raskin JP, Schryvers D, Pardoen T. Dislocation-mediated relaxation in nanograined columnar palladium films revealed by on-chip time-resolved HRTEM testing. Nat Commun 2015; 6:5922. [PMID: 25557273 PMCID: PMC4354052 DOI: 10.1038/ncomms6922] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 11/21/2014] [Indexed: 11/24/2022] Open
Abstract
The high-rate sensitivity of nanostructured metallic materials demonstrated in the recent literature is related to the predominance of thermally activated deformation mechanisms favoured by a large density of internal interfaces. Here we report time-resolved high-resolution electron transmission microscopy creep tests on thin nanograined films using on-chip nanomechanical testing. Tests are performed on palladium, which exhibited unexpectedly large creep rates at room temperature. Despite the small 30-nm grain size, relaxation is found to be mediated by dislocation mechanisms. The dislocations interact with the growth nanotwins present in the grains, leading to a loss of coherency of twin boundaries. The density of stored dislocations first increases with applied deformation, and then decreases with time to drive additional deformation while no grain boundary mechanism is observed. This fast relaxation constitutes a key issue in the development of various micro- and nanotechnologies such as palladium membranes for hydrogen applications. Nanostructured metallic materials involve a high rate sensitivity usually resulting from grain boundary related mechanisms. Here, the authors report mechanical tests on freestanding Pd thin films and show that creep is associated with dislocations rather than grain boundaries.
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Affiliation(s)
- M-S Colla
- Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium
| | - B Amin-Ahmadi
- Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - H Idrissi
- 1] Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium [2] Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - L Malet
- 4MAT: Materials Engineering, Characterization, Synthesis and Recycling, Université Libre de Bruxelles, 50 Avenue FD Roosevelt CP194/03, 1050 Brussels, Belgium
| | - S Godet
- 4MAT: Materials Engineering, Characterization, Synthesis and Recycling, Université Libre de Bruxelles, 50 Avenue FD Roosevelt CP194/03, 1050 Brussels, Belgium
| | - J-P Raskin
- Information and Communications Technologies, Electronics and Applied Mathematics (ICTEAM), Université catholique de Louvain, Place du Levant 3, B-1348 Louvain-la-Neuve, Belgium
| | - D Schryvers
- Department of Physics, Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - T Pardoen
- Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2, B-1348 Louvain-la-Neuve, Belgium
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