Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys

Quasicrystal and It’s Formation Mechanism in As-Cast Mg-Zn-Y Alloy

Author ShiFei
Tutor GuoXueFeng
School Xi'an University of Technology
Course Materials Physics and Chemistry
Keywords Quasicrystals Icosahedral Magnesium alloy Ordinary solidification
CLC TG146.2
Type Master's thesis
Year 2003
Downloads 324
Quotes 6
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In this paper, the ordinary solidification technology to prepare high magnesium, low zinc and low yttrium Mg-Zn-Y lines alloys stable quasicrystalline phase. On this basis, to study the the quasicrystal alloy formation mechanism and distribution characteristics. To provide ideas for future research and preparation of quasicrystalline reinforced situ composites and ultra-high-strength magnesium alloy. The ordinary low Zn and low Y content analysis by optical microscope and SEM solidification microstructure of magnesium alloy; SEM and EDS analysis phase component in the alloy and the solidification of the organization; XRD analysis phase composition of solidification structure; TEM to determine the structure of quasicrystals. The results show that: 1. Mg-Zn-Y ternary alloy melt at room temperature in the cooling process, the quasicrystalline phase directly from the liquid phase nucleation, grow up. The morphology of quasicrystals Not fully grown pentagon, showing a complete five first discovered six petals. Quasi-of Jingjing grain size of less than 50μm. 2. Alloy composition lead to different solidification organization. Mg (69-x) Zn (30 x) Y 1 , Mg 64 Zn 34 < / sub> Y 2 , Mg 70 Zn 28 Y 2 , Mg 71 the zn 27 Y 2 , and Mg 35 Zn 57 Y 8 alloys, resulting from the test solidification structure of α-Mg phase Mg for MgZn matrix precipitates, 30 Zn 60 Y 10 icosahedral quasicrystalline phase; Mg 72.52 Zn 25.48 Y 2 , Mg 74 Zn 24 Y 2 , Mg 76 Zn 22 Y 2 , Mg 66 Zn 31 Y 3 and Mg of 68 Zn 28 alloy the Y- 4 test generated solidification structure for MgZn α-Mg Mg < sub> 30 Zn 60 Y 10 icosahedral quasicrystalline phase eutectic group. 3. Due to the different alloy composition, the cause the quasicrystalline phase morphology, number, size and distribution of the difference. Its own rules, the quasi-crystal grain size, roundness and distribution of the degree of homogenization were increased along with the increase of Y content. In addition, the quasi-crystal show the diversity of morphology. 4. Re-circle the ternary alloy phase diagram of the Mg-Zn-Y icosahedral quasicrystals solidification area marked ideal quasicrystal range. Laid the foundation for further looking for a qualitative analysis of the quasicrystal and quasicrystal.

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