In situ measurement of plasticity accompanying hydrogen induced cracking in a polycrystalline AlZnMg alloy |
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| Affiliation: | 1. Department of Chemical Engineering, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka, 819-0395, Japan;2. Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1 Kichijoji-kitamachi, Musashino-shi, Tokyo, 180-8633, Japan;3. Research Center for Synchrotron Light Applications, Kyushu University, 6-1 Kasuga-koen, Kasuga-shi, Fukuoka, 816-8580, Japan;1. Department of Electronics and Communication Engineering, Vel Tech Rangarajan Dr Sagunthala R&D Institute of Science and Technology, Chennai, Tamil Nadu, 600062, India;2. Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam, 603110, Tamil Nadu, India;3. Centre of Excellence in Water Research (CEWAR), Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam, 603110, Tamil Nadu, India;4. Department of Biotechnology, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences (SIMATS), Chennai, Tamil Nadu, 602105, India;5. Department of Biotechnology, Faculty of Science & Humanities, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, 603203, India;6. Department of Biosciences, Saveetha School of Engineering, SIMATS, Chennai, Tamil Nadu, 602105, India;7. University Centre for Research and Development & Department of Civil Engineering, Chandigarh University, Gharuan, Mohali, Punjab, 140413, India;8. School of Engineering, Lebanese American University, Byblos, Lebanon;1. ENEA - Energy Technologies and Renewable Sources Department (TERIN), ICT Division, Portici Research Center, Piazzale Enrico Fermi 1, Portici 80055, Italy;2. Istituto di Scienze e Tecnologie per l’Energia e la Mobilità Sostenibili - CNR, Viale Marconi 4, 80125 Napoli, Italy;1. Department of Mathematics, National Institute of Technology Agartala, India;2. Mechanical Engineering Department, NIT Agartala Jirania, West Tripura, 799046, India |
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| Abstract: | Hydrogen induced single crack propagation is studied in an embrittled aluminum alloy. Hydrogen is introduced into the system by electrochemical reactions in an acidic aqueous medium. After hydrogen charging, tensile tests are performed in air, on notched samples, with a microtensile machine under an optical microscope. A high magnification of × 2000 is used to follow the single crack initiation and propagation. Digital Image Correlation gives the displacement field on the surface with a spatial resolution of approximately 1 μm. It enables the determination of the position of the crack tip and the local velocity at a sub-grain scale. The von Mises strain is calculated and provides a precise measure of the local plastic field that accompanies crack propagation. In addition to the primary plasticity which is emitted from the crack tip or its immediate neighborhood in the form of two intense slip bands, a secondary plastic zone that spreads over several microns ahead of the tip is sytematically found. The characteristics of the plastic zone are measured, together with the velocity and the applied stress intensity factor. In addition, different fracture mechanisms are found on the fracture surface. In particular there are transitions in the fracture mode from intergranular smooth to transgranular parallel to the grain boundary plane. The local fracture mechanisms, in the vicinity of the surface, are linked to the local velocities and plastic deformations. Surprisingly no strong velocity/plasticity correlations are found while the velocities are scattered over a wide range, which is interpreted as a strong polycrystalline effect. |
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| Keywords: | Micro-mechanics Hydrogen Embrittlement Digital image correlation |
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