• 제목/요약/키워드: Icosahedral quasicrystalline phase

검색결과 4건 처리시간 0.016초

Al-Fe-Mo 합금에서 준결정상의 생성 및 열분해에 관한 연구 (Formation and Thermal Decomposition of a Quasicrystalline Phase in Al-Fe-Mo Alloys)

  • 김석환
    • 열처리공학회지
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    • 제18권6호
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    • pp.362-368
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    • 2005
  • Formation and thermal stability of a quasicrystalline phases in Al-Fe-Mo alloys were investigated by means of melt-spinning process and subsequent heat treatment test. Thermal decomposition and phase transformation process of the as-spun alloys were studied using X-ray diffraction and electron microscopy. The melt-spun Al-Fe-Mo alloys contained an icosahedral quasicrystalline phase with a quasilattice constant of 0.457 nm. Icosahedral phase formed at a composition of $Al_{82.5}Fe_{14}Mo_{3.5}$ as a metastable phase during rapid solidification was transformed into the stable crystalline phases, cubic 1/0 approximant and monoclinic ${\lambda}$-phase, upon heating. A metastable icosahedral and cubic(a = 0.93 nm) phases in as-spun $Al_{65}Fe_{20}Mo_{15}$ alloy were decomposed into two cubic(a = 0.62, 0.31 nm) phases by heat treatment.

나노 준결정상으로 강화된 Ti계 벌크 비정질기지 복합재의 제조 및 기계적 특성 고찰 (Fabrication and Mechanical Properties of Nanoquasicrystalline Phase Reinforced Ti-based Bulk Metallic Glass Matrix Composites)

  • 박진만;임가람;김태응;손성우;김도향
    • 한국주조공학회지
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    • 제28권6호
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    • pp.261-267
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    • 2008
  • In-situ quasicrystalline icosahedral (I) phase reinforced Ti-based bulk metallic glass (BMG) matrix composites have been successfully fabricated by using two distinct thermal histories for BMG forming alloy. The BMG composite containing micron-scale Iphase has been introduced by controlling cooling rate during solidification, whereas nano-scale I-phase reinforced BMG composite has been produced by partial crystallization of BMG. For mechanical properties, micron-scale I-phase distributed BMG composite exhibited lower strength and plasticity compared to the monolithic BMG. On the other hand, nano-scale icosahedral phase embedded BMG composite showed enhanced strength and plasticity. These improved mechanical properties were attributed to the multiplication of shear bands and blocking of the shear band propagation in terms of isolation and homogeneous distribution of nanosize icosahdral phases in the glassy matrix, followed by stabilizing the mechanical and deformation instabilities.

Mg-Zn-Y 합금의 크리프 저항성에 미치는 칼슘의 영향 (Effect of calcium addition on creep properties in Mg-Zn-Y alloys)

  • 이윤희;임현규;김도형;김도향
    • 한국주조공학회지
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    • 제27권5호
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    • pp.198-202
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    • 2007
  • In the present study, the high temperature mechanical properties and creep resistance of Mg-Zn-Y-Ca alloys has been investigated. The Mg-4Zn-0.8Y alloy consists of ${\alpha}$-Mg matrix and icosahedral quasicrystalline phase. Calcium addition into Mg-4n-0.8Y based alloy results in the formation of ${\tau}(Ca_{2}Mg_{6}Zn_{3})$ and $Mg_{2}Ca$ as the second solidification phases. Creep properties of the Mg-Zn-Y and Mg-Zn-Ca based alloys measured at applied stresses between 65 MPa and 85 MPa are significantly improved with adding calcium and yttrium, respectively. The improved creep resistance is due to the formation of thermally stable $Mg_{2}Ca$ phase.

주조용 합금으로서 Mg-Y-X (X=Al or Mm) 합금의 주조성 및 크리프 성질에 관한 연구 (Study on Castability and Creep Properties of Mg-Zn-Y-X (X=Al or Mm) Alloys as Casting Alloy)

  • 임현규;이주연;김원태;김도향
    • 한국주조공학회지
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    • 제26권1호
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    • pp.34-39
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    • 2006
  • In the present study, the possibility of Mg-Zn-Y alloys as high temperature casting alloys has been investigated. The fluidity of alloys containing yttrium were better than that of commercial AZ91 alloy because the oxide layer on the surface reduced the reaction between melt, and air and mold, which would reduce the resistance during the process of filling the mold. However, this oxide film reduced the hot-tearing resistance. In the case of ZAW942, this alloy exhibited fluidity and hot-tearing resistance better than AZ91 alloy. Because of thermally stable quasicrystal and other phases obstructed the movement of grains, the creep resistance of alloys containing rare earth elements more than 2 wt% was better than that of AZ91 alloy.