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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/2816


    Title: 鎂合金之晶粒細化與超塑性研究;Grain Refined and Superplasticity of Magnesium Alloys
    Authors: 彭正球;Cheng-Chiou Peng
    Contributors: 機械工程研究所
    Keywords: 通道彎角擠製;超塑性;superplasticity;equal channel angular extrusion
    Date: 2006-07-04
    Issue Date: 2009-09-21 11:56:56 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 摘要 由於環保意識的抬頭及高油價時代的來臨,如何減少能源的損耗及保 護環境已成為一項重要的課題,而鎂合金具有比重輕,比鋼性大及可回收 等特性,應用於汽車等運輸工具之零件材料以減輕重量,進而節約能源及 減少溫室氣體之排放,最具效益性。另其具備吸收電磁波防電磁干擾、散 熱快及吸震耐摔等性能,更使其成為3C 產業未來發展不可或缺的主角。 鎂合金添加鋰元素,除可降低鎂合金之密度,符合輕量化之要求外,亦可 大幅改善鎂合金之加工性質。 近幾年來,利用等通道彎角擠製(ECAE)技術,以達到晶粒細化目的, 被廣泛的應用於研究許多鎂合金材料上,但是對於Mg-Li-Zn 合金的研究 卻未多見。本研究係針對添加不同合金元素的五種Mg-Li-Zn 合金,分別 施以ECAE 製程,分析其微結構及機械性質,以探討各種ECAE 製程參數對 其微結構及機械性質之影響。 經由實驗之結果觀察分析,可以歸納出如下的幾個主要結論:(1)透 過ECAE 製程,可強化五種Mg-Li-Zn 合金材料之硬度、抗拉強度及降伏強 度等機械性質,而材料之伸長率卻會減少。( 2)通過ECAE 擠製過程,可 以將五種材料之α相予以分割及細化,甚至球化,以阻止β相差排移動, 達到分散強化之目的。(3)第一道次對退火後之五種Mg-Li-Zn 合金材料有 最大的強化效果。(4) 五種Mg-Li-Zn 合金材料在經過四道次之ECAE 擠製 後,LZ91 有最強之降伏強度值。(5)相對於120o彎道夾角之ECAE 製程, 90o彎道夾角對五種Mg-Li-Zn 合金材料機械性質之強化有較顯著的效果。 (6)在超塑性方面:於高溫拉伸測試時,細化之α相可阻止β相晶粒之成 iii 長,可增進材料之超塑性。LZ91 合金於250℃及1×10-4s-1條件下,進行高 溫超塑性拉伸測試,可獲得350%之伸長率。(7)五種合金中之LZ111 合金 及LAZM9310 合金於較高應變速率(高於1×10?3s?1)下有較好的超塑性。 Abstract Because of the emergence of environmental protection consciousness and the coming of high oil price, the energy saving and the green have become the most important subjects in recent years. Magnesium alloys not only have the characteristics of low specific weight, high specific strength, and recycling, but also have great performance on anti-impact and anti-EMI (electronmagnetic interference). Because of these inherent characteristics, magnesium alloys have widely been used in transportation and 3C (computer, communication, and consumer electronic) industries. Besides, doping some lithium in magnesium alloys makes the new magnesium alloys have lower specific weight, higher specific strength, and better machinability. It can be expected that the magnesium alloys with lithium doping will have an important role in the future. ECAE (equal channel angular extrusion) can fine the grain size of materials and widely be used in magnesium alloys researches. However, there are just few literatures discussed the applications of ECAE on Mg-Li-Zn alloys. In this research, it studied the effects of the control parameters of ECAE on the microstructures and mechanical properties of five different Mg-Li-Zn alloys. After collecting, observing, and studying the experiment results, some conclusions had been gotten, and they are stated as below. (1) ECAE can improve the hardness, tension strength, yield strength of these five Mg-Li-Zn alloys but lower their ductility. (2)ECAE can make theα-phase of these five Mg-Li-Zn alloys finer, divided, and even spheralized to prevent the dislocation move of the β-phase and get better strength. (3)The first ECAE process has the greatest strength improvement in the five annealed Mg-Li-Zn alloys. (4)After four times ECAE process, LZ91 has the greatest yield strength. (5)The 90° ECAE process has greater strength improvement in these five Mg-Li-Zn alloys than the 120° one. (6)Because the finer α-phase can stop the growth of theβ-phase to get better superplasticity during high temperature tension test, LZ91 has 350% ductility in the 250℃ and 1x10-3s-1test conditions of the high temperature tension test. (7)In higher stain rate condition ( > 1x10-3s-1), LZ111 and LAZM9310 have better superplasticity among these five Mg-Li-Zn alloys.
    Appears in Collections:[機械工程研究所] 博碩士論文

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