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Vol.53, No.5, 312 ~ 320, 2015
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| Title |
| Effect of Microstructures and Tempering Heat Treatment on the Mechanical Properties of 9Cr-2W Reduced-Activation Ferritic-Martensitic Steel |
| 박민구 Min Gu Park , 문준오 Joon Oh Moon , 이태호 Tae Ho Lee , 강남현 Nam Hyun Kang , 김형찬 Hyoung Chan Kim , 이창훈 Chang Hoon Lee |
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| Abstract |
| The aim of this study was to investigate the effect of microstructures (martensite, ferrite, or mixed ferrite and martensite) on the mechanical properties. Of particular interest was the Charpy impact results for 9Cr-2W reduced-activation ferritic-martensitic (RAFM) steels. Under normalized conditions, steel with martensitic microstructure showed superior tensile strength and Charpy impact results. This may result from auto-tempering during the transformation of martensite. On the other hand, both ferrite, and ferrite mixed with martensite, showed unusually poor Charpy impact results. This is because the ferrite phases, and coarse M23C6 carbides at the ferrite-grain boundaries acted as cleavage crack propagation paths, and as preferential initiation sites for cleavage cracks, respectively. After the tempering heat treatment, although tensile strength decreased, the energy absorbed during the Charpy impact test drastically increased for martensite, and ferrite mixed with martensite. This was due to the tempered martensite. On the other hand, there were no distinctive differences in tensile and Charpy impact properties of steel with ferrite microstructure, when comparing normalized and tempered conditions. |
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| Key Words |
| metals, toughness, impact test, tempering, reduced activation ferritic-martensitic steel |
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