Journal of Korea Foundry Society (한국주조공학회지)

Korea Foundry Society (한국주조공학회)
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Effect of Heat-treatment on Microstructure and Tensile Properties in Cast Alloy 718

주조 합금 Alloy 718에서 미세조직과 인장특성에 미치는 열처리의 영향

  • Do, Jeong-Hyeon (High Temperature Materials Group, Korea Institute of Materials Science) ;
  • Kim, In-Soo (High Temperature Materials Group, Korea Institute of Materials Science) ;
  • Choi, Baig-Gyu (High Temperature Materials Group, Korea Institute of Materials Science) ;
  • Jung, Joong-Eun (High Temperature Materials Group, Korea Institute of Materials Science) ;
  • Jung, In-Yong (High Temperature Materials Group, Korea Institute of Materials Science) ;
  • Jo, Chang-Yong (High Temperature Materials Group, Korea Institute of Materials Science)
  • 도정현 (한국기계연구원 부설 재료연구소 내열재료연구실) ;
  • 김인수 (한국기계연구원 부설 재료연구소 내열재료연구실) ;
  • 최백규 (한국기계연구원 부설 재료연구소 내열재료연구실) ;
  • 정중은 (한국기계연구원 부설 재료연구소 내열재료연구실) ;
  • 정인용 (한국기계연구원 부설 재료연구소 내열재료연구실) ;
  • 조창용 (한국기계연구원 부설 재료연구소 내열재료연구실)
  • Received : 2016.09.22
  • Accepted : 2016.10.25
  • Published : 2016.10.31
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Abstract

The effect of various types of heat-treatment on the mechanical properties of cast Alloy 718 has been investigated. Cast Alloy 718 bars were subjected to 'standard heat-treatment'_(SHT), 'HIP (Hot Isostatic Pressing) heat-treatment'_(HHT), and 'HIP-simulated heat-treatment'_(HS). In the absence of long time high temperature heat-treatment, a small amount of Laves phase remained in the 'SHT' specimen, and needle shaped ${\delta}$ precipitated in the vicinity of the Laves phase. Due to the formation of the Laves and ${\delta}$ phases in the 'SHT' specimen, it exhibited lower tensile properties than those of the others_specimens. On the other hand, the Laves phase was completely dissolved into the matrix after 'HHT' and 'HS' treatments. It is known that isostatic pressure reduces the self-diffusion coefficient, because of the lower self-diffusivity under HIP conditions in the interdendritic region, Nb segregation and the high amount of ${\gamma}^{{\prime}{\prime}}$ precipitation that occurs. Due to the higher fraction of coarse ${\gamma}^{{\prime}{\prime}}$ phases, the 'HHT' treated Alloy 718 showed excellent tensile strength.

Keywords

References

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