添加鈹、鈧之LAZ1110鎂鋰合金經等通道彎角擠製後之微結構及機械性質研究

A study on the Microstructures and Mechanical properties of LAZ1110 Mg-Li alloy containing Sc and Be after Equal Channel Angular Extrusion

劉國政(Guo-Jheng Liou)

指導教授 ： 李雄

國立中央大學/工學院/機械工程學系/碩士(2008年)

摘要

本論文以LAZ1110鎂合金為基本，添加微量Be、Sc元素，形成LAZ1110、LAZ1110+Sc、LAZ1110+Be及LAZ1110＋Be,Sc四種合金，除了觀察添加微量Be、Sc元素對LAZ1110在微結構及機械性質的影響外，亦藉由等通道彎角擠製（ECAE）嘗試細化晶粒及探討擠製後之常溫機械性質、微結構的變化，並對ECAE後材料進行退火處理，觀察微結構及硬度值的變化。
比較四種原材之微結構，LAZ1110合金添加Sc，有晶粒細化的效果。LAZ1110合金添加Be，會產生兩種微結構的影響，晶粒粗大及費德曼組織。在機械性質部分，抗拉強度以LAZ1110+Be最高，達151 MPa，較LAZ1110+Sc的147 MPa高，在此以添加Be產生費德曼組織的析出強化效果較添加Sc的細晶強化好。
四種原材於室溫經ECAE後，LAZ1110合金經120°-RT-C4擠製後，晶粒從25μm細化至11μm，為原材的44%；LAZ1110+Sc合金經120°-RT-C4擠製後，晶粒從18μm細化至9.7μm，為原材的54%；LAZ1110+Be合金經120°-RT-C4擠製後，部分區域出現動態再結晶晶粒組織，大小約為5~20μm，LAZ1110＋Be＆Sc合金經120°-RT-C4擠製後，晶粒大小變化不大。在機械性質部分，最大抗拉強度出現在LAZ1110+Be經120°-RT-C4擠製後，達175.5 MPa，為原材的1.16倍，伸長率仍有69.7％。
四種材料經120°-RT-C4擠製後之試片，施以50、100、150、200及250℃×30min退火處理後，於LAZ1110+Be，250℃×30min退火條件下觀察到大面積的靜態再結晶，晶粒大小約為4.5μm，且費德曼組織消失。而四種材料退火硬度值於50℃呈現下降的趨勢，而後隨著溫度提升而有漸增的趨勢，50-200℃硬度值均呈平緩漸增，至250℃硬度值產生驟增的現象。

關鍵字

鎂鋰鋁鋅合金 ； 等通道彎角擠製 ； 微結構 ； 機械性質

並列摘要

An unprecedented try of adding Sc and Be elements into Mg-Li alloys in order to enhance their strengths has been carried out and the results will be presented. Four Mg-Li alloys; a bare one (11%Li-1%Al-0.5%Zn), the second with Sc, the third with Be and the fourth with both Sc and Be were prepared by vacuum melting processes. They were then homogenized at 350℃, followed by an extrusion for plates. Microstructures and mechanical properties are studied on this as-extruded sample and those subsequently process by equal channel angular extrusion (ECAE) at room temperature.
The effect of adding Sc element to the LAZ1110 alloy was refining β grains. The addition of Be element produces two micro-structural effects, grain coarsening and Widmanstatten structure. On the mechanical properties, the maximum tensile strength obtained in LAZ1110+Be is 151MPa.This figure is better than the other of three alloys.
LAZ1110 alloy processed under condition, 120°-RT-C4, the size of β grains range from 25μm to 11μm. LAZ1110+Sc alloy processed under condition, 120°-RT-C4, the size of β grains range from 18μm to 9.7μm. LAZ1110+Be alloy processed under condition, 120°-RT-C4, some area of β phase can be find dynamic recrystallization grains. LAZ1110+Be&Sc alloy processed under condition, 120°-RT-C4, the change of β grains were small. On the mechanical properties, LAZ1110+Be alloy processed under condition, 120°-RT-C4,shows the greatest increase in tensile strength about 24.8 MPa.

並列關鍵字

Mg-Li-Al-Zn alloys ； Equal channel angular extrusion ； Microstructure ； Mechanical properties

參考文獻

【2】郭子強, 「熱處理對AZ91D鎂合金顯微組織與電化學性質影響之研究」, 國立成功大學, 碩士論文, 民國93年。

【9】C. H. Caceres, C. J. Davidson, J. R. Griffiths and C. L. Newton, “Effects of solidification rate and ageing on the microstructure and mechanical properties of AZ91 alloy”, Materials Science and Engineering A325(2002), pp. 344~355.

【12】A. Bussib, A. Ben Artzy, A. Shtechman, S. Ifergan and M. Kupiec, “Grain refinement of AZ31 and ZK60 Mg alloy-towards superplasticity studies”, Materials Science and Engineering A, 302A(2001), pp.56.

【15】R. Z. Valiev, R. K. Islamgaliev and I. V. Alexandrov, “Bulk nanostructured materials from severe plastic deformation”, Progress in Materials Science, 45 (2000) , pp.103-189.

【17】W. H. HAUNG, L. Chang, P. W. Kao and C. P. Chang, Materials Science and Engineering A 307 (2001), pp.113.