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Title: 釓元素-Gd對Mg-Y-Cu合金玻璃成形能力之影響研究
Effect of Gd Addition on the Glass Forming Ability of Mg-Y-Cu Alloys
Authors: Chi-Ching Hsu
徐麒欽
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: 機械合金;鎂基非晶質合金;稀土元素;結晶活化能;真空熱壓
Mechanical Alloying;Mg-based Amorphous alloy;Rare earth;Crystallization;Vacuum hot pressing
Date: 2003
Issue Date: 2011-06-30T07:22:27Z
Abstract: 本研究主要是探討添加稀土元素Gd對Mg-Y-Cu-Gd非晶質合金系統玻璃形成能力與結晶行為的影響,同時也評估利用真空熱壓法製備Mg-Y-Cu-Gd非晶質合金塊材的可行性。研究結果顯示Mg-Y-Cu-Gd混合粉末經十小時高能量球磨處理後均為非晶質相和部分奈米結晶相的混合組織,以Gd部分取代Mg、Cu、Y的研究發現,利用Gd置換Mg和Y的效果最好;從Mg44Cu36Y15Gd5和Mg49Cu33Y15Gd3合金粉末分別經非恆溫與恆溫熱處理求出之活化能比較,可推斷Mg44Cu36Y15Gd5合金粉末的熱穩定性較佳,又分析非恆溫熱處理所得之數據發現升溫速率與活化能之間有一密切關係存在,升溫速率越高時結晶溫度會隨之提高但活化能則會降低,利用Johnson-Mehl-Avrami(JMA)分析所得到Mg44Cu36Y15Gd5和Mg49Cu33Y15Gd3合金粉末之Avrami exponent (n)值各為2.19和2.17,代表兩合金在結晶化過程中之晶粒成長主要是受到擴散機制的影響且呈現三維方向之成長,惟成核速率呈現逐漸遞減的趨勢,經真空熱壓成型之Mg44Cu36Y15Gd5和Mg49Cu33Y15Gd3非晶質合金塊材的最大孔隙約2∼3μm,其微硬度值分別為418、391 kg/mm2。
The main purpose of this study is to investigate the effect of rare earth addition (Gd) on the glass forming ability (GFA) and crystallization behavior of mechanically alloyed Mg-Y-Cu-Gd powders, in addition, the feasibility of fabricating Mg-Y-Cu-Gd bulk amorphous alloy by vacuum hot pressing was also studied. According to the results, after 10 hours of milling, mechanically alloyed powders exhibited a mixing structure of amorphous /nanocrystalline phase. The improvement on the GFA of mechanically alloyed Mg-Y-Cu-Gd powders can be accompolised by the replacement of Mg and Y with Gd addition. Comparing the result of non-isothermal and isothermal thermal analysis data, it is found that amorphous alloy Mg44Cu36Y15Gd5 has the best thermal stability. The Avrami exponent of amorphous alloy Mg44Cu36Y15Gd5 and Mg49Cu33Y15Gd3 were 2.19 and 2.17 by using Johnson-Mehl-Avrami(JMA) analysis. This implies that the crystallization is governed by diffusion-controlled three-dimensional growth but the nucleation rate shows decreased tendency. The maximum porosity for the hot-pressed Mg44Cu36Y15Gd5 and Mg49Cu33Y15Gd3 bulk sample were around 2~3 μm and the Vickers hardness were 418 and 391 Kg/mm2, respectively.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M91550001
http://ntour.ntou.edu.tw/ir/handle/987654321/13513
Appears in Collections:[Institute of Materials Engineering] Dissertations and Theses

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