鎂合金在金屬成形技術上受到限制的最主要原因是其原子係以六方最密堆積的方式排列。因此鎂合金在室溫下延性非常低、不易成形。而為了增加鎂合金的機械性質，目前有許多的研究使用大量塑性變形法來進行鎂合金機械性質的改善。等徑轉角擠製(Equal channel angular extrusion，ECAE)為眾多大量塑性變形法中最為簡單方便的一種方法，而且ECAE 所需的外力較小，並且可以藉由改變模具參數控制試片的顯微組織。
本研究選用奈米級氧化鋁顆粒(Al2O3p)材料做為強化相，並以攪拌鑄造法的製程將強化相以攪拌的方式融入AZ61熔湯中，最後模具成型。再利用等徑轉角擠製(ECAE)的製程對添加不同氧化鋁顆粒含量的鎂基複合材料進行擠製。由結果顯示，AZ61/5wt%Al2O3p鎂基複合材料的鑄造態，其硬度、降伏強度、極限強度及伸長率均比母材獲得提升。對AZ61/5wt%Al2O3p鎂基複合材料進行ECAE，因動態再結晶及差排之影響，經過四次ECAE擠製後平均晶粒尺寸由27.2μm可均勻細化至5.1μm。
AZ61鎂基複合材料的強度以及延性皆會隨著ECAE 次數的增加而明顯提升，本實驗四次ECAE 後，可獲得最佳的為性質AZ61鎂合金添加5wt%Al2O3p：硬度值由鑄錠的69HV 增加至97.6HV;拉伸性質的部分，最大抗拉強度由242.3MPa 增加至335.4MPa；降伏強度由95.5MPa 增加至168.3MPa；延展率由15%增加至25%。
疲勞性質方面，複材隨著顆粒重量百分比的增加，壽命也有明顯的提升，本實驗AZ61加入5wt%Al2O3p經過ECAE擠製後，當最大負載72MPa，應力比為0.1，擁有最高的壽命高達618236 cycles。
由強化機制之貢獻度計算後，可得知熱膨脹係數差異影響最大，而Hall-Petch之晶粒強化次之，Orowan之散步強化第三。

This paper studies the mechanical properties enhancement of AZ61/Al2O3p magnesium metal-matrix nanocomposites by different manufacturing process. Equal Channel Angular Extrusion (ECAE) is a useful technique to produce bulk nano-structured materials by severe plastic deformation. The present magnesium metal matrix composites (Mg MMCs) with 1, 2 and 5 wt% of nano-sized Al2O3 particulates for ECAE were fabricated using stir-casting method. Observing the microstructures of MMCs, the more uniform microstructure consisting of grains with a average grain size of ~5μm is observed in the AZ61/5wt% Al2O3p MMC after 4 passes of ECAE. The hardness of MMCs increased evidently with the increase of the weight percentage of Al2O3p additions and ECAE passes. The optimal hardness of AZ61/5wt% Al2O3p MMC after 4 passes has increased to 97.6 HV. The tensile property of MMCs increased evidently with the increase of the weight percentage of Al2O3p additions and ECAE passes. The ultimate strength of AZ61/5wt% Al2O3p MMC after 4 passes has increased to 335.4 MPa. The life of AZ61/5wt% Al2O3p MMC after 4 passes has increased to 618236 cycles.

[1] R. Kaibyshev, F. Musin, D.R. Lesuer and T.G. Nieh, “Superplastic behavior of an Al-Mg alloy at elevated temperatures”, Material Science and Engineering, A342, pp.169-177, 2003
[2] J. Zrnik, V. Dobatkin and Mamuzic, “processing of metals by severe plastic deformation (spd) – structure and mechanical properties respond”, metabk 47(3) pp.211-216, 2008
[3] Toshiji Mukai, Masataka kawazoe and Kenji Higashi, “ Dynamic mechanical
properties of a near-nano aluminum alloy processed by Equal-Cannel-Angular-E xtrusion” Nano Structured Materials , pp.755-765,1998
[4] 楊仁豪，”AZ31鎂合金經ECAE後晶粒細化與超塑性之研究”，國立交通大學材料科學與工程研究所碩士論文，2001
[5] M. Manoharan, S.C.V. Lim and M. Gupta, “Application of a model for the work
hardening behavior to Mg/SiC composites synthesized using a fluxless casting process”, Materials Science and Engineering ,A333, pp.243-249, 2002.
[6] S.F. Hassan and M. Gupta, “Effect of particulate size of Al2O3 reinforcement on microstructure and mechanical behavior of solidification processed elemental Mg”, Journal of Alloys and Compounds 419 ,pp.84-90,2006
[7] B.W. Chua, L. Lu and M.O. Lai,“Influence of SiC particles on mechanical properties of Mg based Composite”, Composite Structures 47,pp.595-601, 1999.
[8] 康永林、王朝輝，”半固態工藝製備奈米SiC顆粒增強AM60鎂合金的研究，特種鑄造及有色合金”，2007
[9] M. Paramsothy, S.F. Hassan, N. Srikanth and M. Gupta, “Enhancing tensile/compressive response of magnesium alloy AZ31 by integrating with Al2O3 nanoparticles”, Materials Science and Engineering ,A 527,pp.162–168,2009
[10] Wang Xiao-jun, Hu Xiao-shi, NIE Kai-bo, Wu Kun and Zheng Ming-yi, “Effect of hot extrusion on microstructures and mechanical properties of SiC nanoparticles reinforced magnesium matrix composite”, Journal of Alloys and Compounds 512, pp.355-360,2012
[11] Muhammad Shahzad and Lothar Wagner,“ Influence of extrusion parameters on microstructure and texture developments, and their effects on mechanical properties of the magnesium alloy AZ80”, Materials Science and Engineering A 506,pp.141-147 ,2009
[12] 戴國政， MRI 鎂合金高溫高週疲勞特性之研究，逢甲大學機械工程研究所論文,2007
[13] V.M. Segal, “ Materials processing by simple shear”, Materials Science and Engineering A197, pp.157–164,1995
[14] C ,Pithana , T, Hashimotoa, M ,Kawazoea and J, Nagahoraa, “Microstructure and texture evolution in ECAE processed A5056” Materials Science and Engineering A280,pp.62–68,2000
[15] M. Furukawa﹐Y. Iwahashi﹐Z. Horita﹐M. Nemoto and T. G.Langdon﹐“The shearing characteristics associated with equal-channel angular pressing”,Materials Science and Engineering A257,pp.328,1998
[16] Y. Iwahashi﹐Z. Horita﹐M. Nemoto and T. G. Langdon ,“The process of grain refinement in equal-channel angular pressing”﹐ActaMater.46,pp.3317,1998
[17] K. Oh-ishi﹐Z. Horita﹐M. Furukawa﹐M. Nemoto and T. G. Langdon “Optimizing the Rotation Conditions for Grain Refinement in Equal-Channel Angular Pressing”﹐Metall.Trans. A29,pp.2245,1998
[18] F. Kang, J. T. Wang and Y. Peng, “Deformation and Fracture during Equal Channel Angular Pressing of AZ31 Magnesium Alloy”, Materials Science and Engineering A487, pp. 68-73, 2008
[19] Qiang Chen, Zhixiang Zhao, Dayu Shu and Zude Zhao, “Microstructure and mechanical properties of AZ91D magnesium alloy prepared by compound extrusion”, Materials Science and Engineering A 528,pp 3930–3934,2011
[20] K. Matsubara, Y. Miyahara, Z. Horita and T. G. Langdon, “Developing Superplasticity in a Magnesium Alloy through a Combination of Extrusion and ECAP”, Acta Mater. 51, pp. 3073-3084, 2003
[21] Arne K. Dahle, Young C. Lee, Mark D. Nave, Paul L. Schaffer and David H StJohn, “Development of the as-cast microstructure in magnesium- aluminium alloys” Journal of Light Metals 1, pp.61-72, 2001
[22] 洪大凡, AZ61鎂合金管材之熱擠成形性探討, 國立台灣科技大學機械工程系碩士論文, 2006.
[23] 陳振華，“鎂合金”，化學工業出版社，2004 年 4月
[24] M. Habibnejad-Korayem, R. Mahmudi and W.J. Poole, Enhanced properties of Mg-based nano-composites reinforced with Al2O3 nano-particles, Materials Science and Engineering A 519,pp198–203, 2009
[25] M. Furekawa, Y. Iwahashi, Z. Horita, M. Nemoto and T. G. Langdon, “The Shearing Characteristics associated with Equal Channel Angular Pressing”, Materials Science and Engineering, A257, pp. 328-332, 1998
[26] C. Pithan, T. Hashimoto, M. Kawazoe, J. Nagahora and K. Higashi, “Microstructure and Texture Evolution in ECAE Processed A5056”, Materials Science and Engineering, A280, pp. 62-68, 2000
[27] 黃友聖，AZ61/SiCp鎂基複合材料擠型製程及其擠型管之機械性質研究，國立中正大學機械工程學系研究所碩士論文，2010。
[28] 劉彥辰，AM60/Al2O3p鎂基複合材料擠型管之機械性質與微觀組織研究，國立中正大學機械工程學系研究所碩士論文，2011。
[29] 袁成華，鈦鉬合金熱處理後疲勞性質之研究，國立成功大學材料科學與工程學系研究所碩士論文，2003。
[30] 許育銓，SA533 B1 壓力槽鋼材之高週疲勞壽限評估模式研究，國立中央大 學機械工程研究所碩士論文，2001
[31] 簡嘉毅，鈦-鉬合金熱處理後拉伸疲勞性質研究，國立成功大學材料科學與工程學系研究所碩士論文，2005
[32] A. Sanaty-Zadeh, “ Comparison between current models for the strength of particulate-reinforced metal matrix nanocomposites with emphasis on consideration of Hall–Petch effect” ,Materials Science and Engineering. Eng, A531, pp.112-118,2012
[33] Song-Jeng Huang and Po-Chou Lin , “Grain refinement of AM60/Al2O3p Magnesium metal-matrix composites processed by ECAE”, Metallic Material,2013
[34] C.S. Goh, J. Wei, L.C. Lee, and M. Gupta: Acta Mater., 55, 2007,pp.5115.
[35] Z. Zhang and D.L. Chen: Mater. Sci. Eng., A, 483, 2008,pp.148.
[36] 蔡錫堯，“材料試驗”，總經銷大揚出版社，1997年 2月
[37] Julie Bannantine , Jess Comer and James Handrock, “Fundamentals of metal fatigue analsis”,1990
[38] 鐘仕豪，超輕鎂鋰合金的拉伸與疲勞特性之研究，國立中央大 學機械工程研究所碩士論文，2010