Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy

The Preparation and Properties of Quasicrystalline Mg-Zn-Y Alloys

Author YangMengLei
Tutor YuFengXia;WangLiMin
School Changchun University of Science and Technology
Course Materials Science
Keywords Mg-Zn - Y alloy Icosahedral quasicrystals Cooling rate Hydrogen Storage Discharge capacity
CLC TG139
Type Master's thesis
Year 2007
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This study used a variety of methods to prepare the Department of Mg - Zn - Y quasicrystals . Alloy composition designed to Mg 42 Zn 50 Y 8 . The results showed that different pouring temperature and cooling rate the Zn in the Mg 42 < / sub > 50 < / sub > Y of 8 < / sub > alloys have a lot of quasicrystals generated . XRD analysis showed that Mg 42 Zn 50 Y 8 alloy phase icosahedral quasicrystalline phase and the low temperature phase . Quasicrystalline phase composition is approximately Mg Zn of 30 60 Y 10 < / sub > , the low-temperature phase component approximately Mg 70 < / sub > Zn 30 . The icosahedral quasicrystals morphology irregular petal-shaped or polygonal shape . Quasicrystal external conditions have a greater impact at the crystal morphology of the cooling rate at the crystal morphology is relatively large, the greater the cooling rate of quasicrystals more small petals . TEM analysis can be found in its special five symmetrical structure . Quasicrystal growth determinants special quasi-periodic structure , a lot of quasicrystals can be generated in the quenching conditions , but too fast cooling rate is not conducive to generate quasicrystalline phase in Mg - Zn - Y alloys by rapid solidification generated when the quench phase is Mg 10 Y 2 Zn crystalline and amorphous phases . The hydrogen storage properties of the alloy can accommodate the type and number of the hydrogen clearance vary depending on the alloy and the electrochemical reaction of hydrogen and alloys . Quasicrystalline phase has can accommodate a large number of hydrogen tetrahedral structure and reaction with hydrogen Mg and Y elements , in theory has better hydrogen storage properties . In this study, the Mg - Zn - Y quasicrystal as Ni-MH battery negative electrochemical hydrogen storage performance . The results showed that the quasicrystalline alloy at room temperature is a less activation of the alloy , and the absorption and desorption kinetics of hydrogen poor, low discharge capacity at room temperature , but as the temperature increases the discharge capacity of the alloy greatly improved , but its cycle life along with attenuation. Analysis with Mg element higher absorption and desorption of hydrogen temperature , poor corrosion resistance related . The paper also explored the impact of temperature and electrolyte concentration at the the crystalline alloy electrode performance .

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