鎂鋅鋁準晶相之合成及其結構變化

Synthesis and Structural Transformations of Mg-Zn-Al Quasicrystalline Phase

郭孟鑫(Meng-Hsin Kuo)

指導教授 ： 吳新明

大同大學/工程學院/材料工程學系所/碩士(2005年)

摘要

本研究以機械合金化法製備Mg-Zn-Al三元系統各中間相及準晶粉末，以X-ray繞射及熱分析為主要分析工具，探討用非固態平衡法合成Mg-Zn-Al各中間相及準晶相的成分範圍及其條件。本研究探討在Mg-Zn-Al三元相圖靠近相及相附近成分的球磨及其退火之行為。對於成分Mg55Zn22.5Al22.5，在球磨至2.5小時後發現了二十面體準晶相之生成。在最初起始粉末中之Mg、Zn、Al相對含量影響球磨合金化之行為並不相同。本研究顯示諸如機械合金化法之非平衡固態球磨方式可經由非化學記量成分獲得二十面體準晶相。在最初粉末中隨著Zn含量之增加，經球磨後之粉末退火所得之平衡結構為MgZn2。在另一方面，隨著Al含量之增加，Mg32(Al,Zn)49為退火後之平衡結構。球磨後之粉末在較低溫退火產生MgZn2相，此相在較高溫下退火將轉變為Mg32(Al,Zn)49，也就是說，Mg32(Al,Zn)49相為經由MgZn2相在較高溫下轉變而成。

關鍵字

機械合金化法，中間相，相變化，Mg -Zn-Al三元系。

並列摘要

In this research it is intended to synthesize the powders of various intermediate phases and icosahedral quasicrystal in Mg-Zn-Al system by mechanical alloying (MA) technique. With X-ray diffraction and thermal analysis as the analytical tools, the composition ranges and formation conditions of the various intermediate and quasicrystalline phases in the Mg-Al-Zn system synthesized by MA were investigated in this study. The milling and annealing behavior of Mg-Zn-Al ternary powders in the composition ranges in the neighborhood of the  phase and  phase were investigated. For composition of Mg55Zn22.5Al22.5, the icosahedral quasicrystalline phase starts to appear when the milling was lasted for 2.5 hr. It seems that the relative contents of Mg, Zn and Al in the starting powders might affect the alloying behavior in a quite different way. Non-equilibrium solid-state milling like mechanical alloying can create the i-phase from the non-stoichiometric composition. With increase in Zn content in the initial powder composition, the equilibrium structure obtained after annealing the milled powders is the MgZn2 phase. On the other hand, with increase in Al content, Mg32(Al,Zn)49 is the structure obtained after annealing. The annealing of the milled powders at lower temperature creates MgZn2 phase. However, this phase is converted to Mg32(Al,Zn)49 phase upon annealing at higher temperature. Namely the Mg32(Al,Zn)49 phase is obtained through transforming the MgZn2 phase at higher temperature.

並列關鍵字

intermediate phase ； Mechanical alloying ； Mg -Zn-Al system. ； phase transformation

參考文獻

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