Correlation between microstructure evolution and cryogenic fracture toughness in aging ITER-grade 316LN weldments |
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| Affiliation: | 1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China;2. University of Science and Technology of China, Hefei 230026, China;3. State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China;1. Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 200031, China;2. Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta, Finland;1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031, China;2. University of Science and Technology of China, Hefei, 230026, China;3. State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China;1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China;2. University of Science and Technology of China, Hefei 230026, China;3. State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China;4. Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China;1. Institute of Process Equipment, Zhejiang University, Zheda Rd. 38, 310027 Hangzhou, PR China;2. Institute of Applied Mechanics, Zhejiang University, Zheda Rd. 38, 310027 Hangzhou, PR China;3. State Key Laboratory of Fluid Power & Mechatronic Systems, Zhejiang University, Zheda Rd. 38, 310027 Hangzhou, PR China;4. High Pressure Process Equipment and Safety Engineering Research Center of Ministry of Education, Zhejiang University, Zheda Rd. 38, 310027 Hangzhou, PR China;5. China Academy of Safety Science and Technology, Beiyuan Rd. 32, 100012 Beijing, PR China |
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| Abstract: | In the present work, the correlation between microstructural evolution and fracture toughness in 316LN joints welded by Tungsten Inert Gas (TIG) was investigated. The effect of post-weld heat treatment (PWHT) on the microstructure and toughness was characterized. The welding process can significantly change the equiaxed grains of base metal to cells and dendrites, while the PWHT can increase the dendrite size, mitigate the texutre intensity, reduce the dislocation density, and slightly weaken the ultimate tensile strength of the joints. Fracture toughness tests reveal that the strain-induced martensitic transformation at cryogenic temperatures can remarkably deteriorate the fracture toughness. Due to the microstructural evolution during PWHT, the J-integral values at 77 K and 4.2 K decrese to 85% and 54% of those in the as-welded conditions, respectively. The fracture morphology of the as-welded joint shows a characterization of ductile fracture, while the PWHT joint features a mixture of ductile and brittle fracture. |
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| Keywords: | 316LN weldment Post-weld heat treatment Microstructure Mechanical properties Fracture toughness |
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