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Grain Growth Behavior of Heat Treated Mg-0.6wt.%Zn-0.6wt.%Ca Alloy Sheet Manufactured via Twin Roll Casting and Hot Rolling

트윈롤 주조 후 열간압연된 Mg-0.6wt.%Zn-0.6wt.%Ca 합금 판재의 열처리에 따른 결정립 성장 거동

  • Lee, Hee Jae (School of Advanced Materials Science and Engineering, Kumoh National Institute of Technology (KIT)) ;
  • Park, No Jin (School of Advanced Materials Science and Engineering, Kumoh National Institute of Technology (KIT))
  • 이희재 (금오공과대학교 신소재공학부) ;
  • 박노진 (금오공과대학교 신소재공학부)
  • Received : 2022.03.10
  • Accepted : 2022.03.21
  • Published : 2022.03.30

Abstract

This study aims to mitigate the microstructural heterogeneity arising from the manufacture of magnesium alloy plates using the twin roll casting (TRC) process. Homogenization was introduced through hot rolling and heat treatment, followed by confirmation of observed changes in the microstructure. Following the TRC process, the hot rolled 2mm plate exhibited a dendritic cast structure tilted in the roll rotation direction, while central segregation were developed. This nonuniform structure and central segregation disappeared upon heat treatment, followed by recrystallization to form uniform and fine grains. Abnormal grain growth (AGG) was observed over the course of heat treatment; grains exhibiting AGG occupied up to 75% of the total area after having held the sample at 400℃ for 64 h. The formation of coarse grains was also observed during heat treatment at 340℃ over a relatively long duration, though the maximum grain size was significantly smaller than that corresponding to the heat treatment at 400℃. AGG in the 400℃ heat treatment occurred because of movement of the grain boundary, which had been fixed prior as a result of the grain boundary fixing effect of the precipitation phase. The re-dissolution of the Ca2Mg5Zn5 precipitated phase over the long duration of the high-temperature annealing process caused the surrounding grains to disappear and regrow.

Keywords

Acknowledgement

이 연구는 금오공과대학교 학술연구비로 지원되었음(202001460001).

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