Effect of center microstructure on fracture mechanism of ultra-thick high strength steel |
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Authors: | ZHOU Songbo ZHANG Liqin HU Feng YIN Chaochao ZHOU Wen WU Kaiming |
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Affiliation: | 1.Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology,Wuhan 430081, Hubei, China;2.Department of Applied Physics, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China;3.Metals Valley and Band Metallic(Foshan) Composite Materials Co., Ltd., Foshan 528000, Guangdong, China |
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Abstract: | In order to study the relationship between microstructure and fracture mechanism of ultra-thick steel plate, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were used to characterize and analyze the microstructure and crack morphology of 1/4 and 1/2 thickness (center) of the test plate. The results show that the low temperature impact toughness at the center is significantly lower than that at the 1/4 thickness, which is due to the microstructure of the center is tempered lath bainite and tempered granular bainite, and the proportion of granular bainite is higher. The presence of M-A island in granular bainite promotes the initiation of micro pores or micro cracks. The 1/4 thickness is a mixed microstructure of tempered lath martensite and tempered lath bainite. The dislocation movement between laths releases local stress concentration, and relieves the stress at the crack tip region, resulting in crack passivation, hindering crack propagation and improving low temperature impact toughness. |
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Keywords: | Key words:ultra thick steel plate microstructure fracture crack propagation dislocation |
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