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TEM Study on the Healing of Crack Induced by Hydrogen in Carbon Steel |
Chaofang Dong;Xiaogang Li;; |
北京科技大学 |
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Abstract The microstructures of the crack induced by hydrogen and crack healing have been studied by using the transmission electron microscopy(TEM).These specimens of carbon steel with the hydrogeninduced cracks were cyclically annealed at 1000℃ for 10 h.The SEM and TEM observations on the specimens before and after the heat treatment showed that the cracks could be healed completely by heat treatment.The healing of hydrogeninduced cracks was closely related to heat diffusion of Fe and C atoms.The driving force of crack healing resulted from the plastic deformation energy Es created by the growth of hydrogen bubbles or cracks.The critical condition of healing of bubbles or cracks isEs≥2γ/r(whereγis the surface tension,r is the half length of crack).During healing of the hydrogeninduced cracks,the dislocation density around grain boundaries decreased and the dislocation type transformed from tangle dislocation with high energy to vertical and regular dislocation with low energy.The formation of pearlite in distinct layers during healing process indicated the structure of carbon steel recovered too.
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Received: 15 August 2002
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Corresponding Authors:
Chaofang Dong
E-mail: dongchf@sina.com
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