Toughness improvement by Zr addition in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels |
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| Authors: | Yu Liu Guangqiang Li Xianguang Zhang Yu Shen Kaiming Wu |
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| Affiliation: | 1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, China;2. Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, China;3. International Research Institute for Steel Technology, Wuhan University of Science and Technology, Wuhan, China;4. Institute for Materials Research, Tohoku University, Sendai, Japan;5. Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, China |
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| Abstract: | The effect of Zr addition on the microstructure and impact toughness in the coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels subjected to 100?kJ?cm-1 heat input was investigated. The second- phase particles were mainly Al–Ti complex oxides and (Ti,Nb)N precipitates in Zr-free steel, whereas lots of finer Zr–Al–Ti complex oxides and (Al,Ti,Nb)N precipitates were formed in Zr-bearing steel because of Zr addition. These finer oxides and precipitates effectively restricted the austenite grain growth by pinning effect during welding thermal cycle, and smaller and more uniform prior austenite grains were obtained in CGHAZ of Zr-bearing steel. Furthermore, more acicular ferrite grains nucleated on Zr–Al–Ti complex oxides, inducing formation of fine-grained microstructure in CGHAZ of Zr-bearing steel. The toughness improvement in CGHAZ of Zr-bearing steel with dimple fracture surface was attributed to the grain refinement by pinning effect and acicular ferrite formation. |
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| Keywords: | CGHAZ impact toughness particles acicular ferrite fracture |
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