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Vol.53, No.1, 1 ~ 13, 2015
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| Title |
| Formation of Serrated Grain Boundaries and Its Effect on Tensile Properties at 950 ℃ in Alloy 617 for Very High Temperature Reactor |
| 최준우 June Woo Choi , 이지원 Ji Won Lee , 이재현 Je Hyun Lee , 김동진 Dong Jin Kim , 홍현욱 Hyun Uk Hong |
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| Abstract |
| The effects of initial microstructures controlled by thermo-mechanical treatment on tensile properties at 950 ℃ were investigated in Alloy 617. Proprietary direct aging combined with a controlled cooling rate led successfully to the transition of serrated grain boundaries (GBs) with a proportion of over 80%. It was newly found that at an initial stage of the transition, the serrated GBs formed without the presence of carbide or a γ` phase in the solid-solution-strengthened Alloy 617. The serrated GBs with stable planar M23C6 carbides enhanced the uniform elongation while the strength was maintained due to higher resistance to GB cavitational cracking. The fine intragranular carbides, which precipitated substantially through preliminary 5% cold work treatment, were responsible for the strong hardening effect by inhibiting dislocation movement. Based on the results, we propose the initial microstructure for better tensile properties at 950 ℃. (Received January 6, 2014) |
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| Key Words |
| alloys, thermomechanical processing, grain boundary, serration, tensile test |
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