Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Microstructural Characteristics and Hardness of Discontinuous Precipitates Formed by Continuous Cooling and Isothermal Aging in Mg-Al Alloy

Mg-Al 합금에서 연속 냉각 및 등온 시효로 생성된 불연속 석출물의 미세조직 특징과 경도

  • Jun, Joong-Hwan (Advanced Materials and Process R&D Department, Korea Institute of Industrial Technology)
  • 전중환 (한국생산기술연구원 융합소재공정연구부문)
  • Received : 2020.06.15
  • Accepted : 2020.06.29
  • Published : 2020.07.30
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Abstract

The purpose of this study was to investigate comparatively the microstructural characteristics and hardness of discontinuous precipitates (DPs) in Mg-9%Al alloy, which were formed by continuous cooling (CC) from 678 K to RT and isothermal aging (IA) at 413 K, respectively. In as-cast state, the Mg-9%Al alloy consisted of partially divorced eutectic β(Mg17Al12) particles with a small amount of DPs showing (α+β) lamellar morphology adjacent to the β particles. The DPs formed by CC had interlamellar spacings in a broad range of 0.85~2.12 ㎛ (1.51 ㎛ in average) owing to the various formation temperatures in response to continuous cooling process. Meanwhile, the DPs formed by IA had relatively narrower interlamellar spacings of 0.14~0.29 ㎛ (0.21 ㎛ in average), which is associated with the low and constant formation temperature. Thinner and higher volume fraction of β phase layers were noticeable in the DPs formed by IA. Higher hardness values were obtained in the DPs formed by IA than the DPs formed by CC, which may well be ascribed to the finer lamellar structure and higher β phase content of the DPs formed by IA.

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References

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