Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Effect of Cooling Rate on Lamellar Structure and Hardness of Discontinuous Precipitates in Mg-Al-Zn Alloy

Mg-Al-Zn 합금에서 불연속 석출물의 층상 구조와 경도에 미치는 냉각 속도의 영향

  • Jun, Joong-Hwan (Advanced Materials and Process R&D Department, Korea Institute of Industrial Technology)
  • 전중환 (한국생산기술연구원 융합소재공정연구부문)
  • Received : 2020.10.05
  • Accepted : 2020.10.19
  • Published : 2020.11.30
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Abstract

The relationship between the hardness and interlamellar spacing of discontinuous precipitates (DPs) formed by continuous cooling was studied for Mg-9%Al-1%Zn alloy. After solution treatment at 683 K for 24 h, the specimens were cooled to room temperature with different cooling rates ranging from 0.2 to 2 K·min-1, in order to obtain DPs with various interlamellar spacings. It was found that cooling rate of 2 K·min-1 yielded only small amount of nodular DPs at the grain boundaries, while cooling rates below 2 K·min-1 yielded both DPs and continuous precipitates (CPs). The volume fraction of DPs increased with increasing cooling rate up to 0.5 K·min-1, over which it abruptly decreased. The hardness of DPs was increased with an increase in the cooling rate, whereas the interlamellar spacing of the DPs was decreased with respect to cooling rate. The hardness of the DPs formed by continuous cooling was correlated with the interlamellar spacing and can follow a Hall-Petch type relation as in the case of pearlite with lamellar morphology.

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References

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