鎂合金具有低密度、高比強度、回收性佳等優點，因而普遍使用在交通工業、3C產業上，但是由於鎂具有HCP結構而使得室溫的成形性不佳，加工需在高溫環境中導致成本較高。故使用摩擦攪拌製程（Friction Stir Process, FSP）作改質，可以獲得再結晶之細小晶粒，以得到較好之加工性。為釐清FSP後組織特徵、織構及洋蔥環效應，本研究以AZ31鎂合金為材料，先進行完全退火處理成為AZ31-O材，之後施以FSP，再分別進行顯微組織觀察、拉伸試驗及振動試驗，以了解織構及洋蔥環效應對機械性質所造成的影響。
在顯微組織方面，AZ31-O經過FSP後組織可區分成SZ-top及SZ-bottom兩個部份。SZ-top具有極明顯的晶粒細化效果，硬度也有顯著的提升；SZ-bottom的晶粒徑則和AZ31-O的接近，而硬度略高於母材。並由XRD的結果顯示，銲道區內的織構如文獻所提相同，皆為HCP的基面沿著攪拌棒的凸梢圓周排列。
之後將FSP後試片分別取樣平行及垂直於改質方向做為拉伸試片，再與母材的拉伸結果做比較，以探討織構對於拉伸性質的影響。結果顯示：平行改質方向拉伸之延性明顯優於母材，但降伏強度以及變形阻抗皆明顯降低；垂直於改質方向拉伸之降伏強度較高，但是延性明顯劣化，僅剩下約8%左右的總延伸率。
針對平行和垂直改質方向的FSP試片及母材進行振動試驗，由相近初始偏移量之共振壽命結果可得到：垂直改質方向的FSP試片壽命約等於母材，且大於平行改質方向的FSP試片。因為平行於改質方向的FSP試片受到洋蔥環效應的影響而使裂紋傳播阻抗最差；垂直改質方向的FSP試片則受到洋蔥環效應及塑性變形能兩個效應的影響所以共振壽命與母材幾乎相同。

Magnesium alloys have several advantages including low density, high specific strength and well recyclabilty. There are common applica- tions in traffic and 3C industry. Magnesium alloys are the hexagonal close-packed (HCP) structure and have bad workability at room tempe- rature (RT). High temperature forming is applied in general, hence it would cause more cost. Therefore, mechanical properties are improved by Friction Stir Process (FSP), and would get fine recrystallized grain to in- crease workability. Full-annealed magnesium alloys of AZ31 (AZ31-O) are processed by FSP. In order to study the effect of microstructure, texture, and onion rings by FSP, the sample of before and after FSP are both studied by tensile test and vibration test. The relationship of the texture distribution, the onion rings and mechanical properties of a FSP AZ31 alloy is discussed.
In the microstructure of FSP AZ31 Mg alloys, there are two parts in- cluding SZ-top and SZ-bottom in the stirred zone (SZ). The hardness of SZ-top increases significantly because the grain size of SZ-top is much smaller than AZ31-O. The hardness of SZ-bottom is improved a little because the grain size of SZ-top is similar to that of AZ31-O. The results are in a texture which the basal plane normal is roughly surrounding the rotation pin surface by X-ray diffraction (XRD). This is similar to the re- ferences.
On tensile test, there are two different directions where the tensile directions are parallel and perpendicular to the processing direction of FSP AZ31, and the results are compared with that of AZ31-O. The experi- mental results indicate that FSP-parallel has better elongation and worse strength. FSP- perpendicular has better yielding stress but it has the worst total elongation which is only 8%.
AZ31-O, FSP- perpendicular and FSP-parallel are used on vibration test. The result of vibration under the condition of constant initial deflect- tion indicates test performed that the better is AZ31-O and FSP- perpen- dicular and that of FSP-parallel is the worst. The vibration fracture resis- tance of FSP-parallel is worst because of the onion ring effect. The vibra- tion life of AZ31-O is similar to FSP- perpendicular because of the effects of the onion rings and the plastic strain energy.

1. 陳錦修，『鎂合金在汽車工業之應用』，工業材料雜誌186期，民國91年6月，148-152頁。
2. 張惠冠，『我國自行車產業發展現況與趨勢分析』，工業材料雜誌188期，民國91年8月，140-144頁。
3. I. J. Polmear, “Recent Developments in Light Alloys”, Mater. Trans, JIM., Vol.37(1), 1996, pp.12-31.
4. I. J. Polmear, “Magnesium Alloys and Applications”, Mater. Sci. Technol., Vol.10(1), 1994, pp.1-15.
5. M. M. Avedesian and H. Baker, “ASM Specialty Handbook- Magnesium and Magnesium Alloys”, ASM Metals Park, OH, 1999, pp. 13-43.
6. M. M. Avedesian and H. Baker, “ASM Specialty Handbook- Magnesium and Magnesium Alooys”, ASM Metals Park, OH, 1999, pp.13-43.
7. 蔡幸甫，『鎂合金產業技術及市場發展趨勢專題調查』，民國90年10月，2-5頁。
8. Michael M. Avedesian and Noranda Magnesium Inc., ASM Specialty Handbook, “Magnesium and Magnesium Alloys”, publish by The Materials Information Socie., pp.14-15.
9. W. M. Thomas, E. D. Nicholas, J. C. Needham, M. G. Murch, P. TempleSmith and C. J. Dawes, “Friction stir butt Welding”, International Patent Application, No.PCT/GB92/02203 and GB Patent Application, No. 9125978. 8, 1991.
10.Y. Li, L. E. Murr and J. C. McClure, “Solid-State Flow visualization in Friction-Stir Welding of 2024 Al to 6061 Al”, Scripta Mater., Vol.40. No.9, 1999, pp.1041-1046.
11.B. Yang, J. Yan, M. A.Sutton and A. P. Reynolds, “Banded Microstrucure in AA2024-T351 and AA2524-T351 Aluminum Friction Stir Welds Part I.Metallurgical studies”, Mater. Scie. and Eng., A356. 2004. pp.55-65.
12.M. A. Suuon, B. Yang, A. P. Reynolds and J. Yan, “Banded Microstructure in AA2024-T351 and AA2524-T351 Aluminum Friction Stir Welds Part II. Mechanical characterization”, Mater. Scie. and Eng., A, Vol.364, 2004, pp.66-74.
13.R. S. Mishra, M. W. Mahonry, S. X. McFadden, N. A. Mara and A. K. Mukherjee, “High Strain Rate Superplasticity in a Friction Stir Processed 7075 Al Alloy”, Scripta Mater,, Vol.42, 2000, pp. 163-168.
14.Z. Y. Ma, R. S. Mishra and M/W/Mahoney, “Superplastic Deformation Behavior of Frition Stir Processed 7075 Al Alloy”, Acta Mater., Vol.50, 2002, pp.4419-4430.
15.Uday Chakkingal.Arief B.and P.F. Thomson. “Microstructure Development During Equal Channel Angular Drawing of Al At Room Temprature”, Scripta Mater., Vol.39, No.6, 1998. pp.677-684.
16.O. Engler, X. W. Kong and K. Lucke, “Recrystallization Textures of Particle-Containing Al-Cu and Al-Mn Single Crystals”, Acta Metall., Vol.49. No.10, 2001, pp.1701-1715.
17.S. Benavifes, Y. Li And L. E. Murr, in“Ultrafine Grained Materials”, Edited by R. S. Mishra, S. L. Semiatin, C. Suryanarayana, N. N. Thadhani and T. C. Lowe (TMS. Warrendale. PA. 2000) .pp.155.
18.W. Woo, H. Choo, D. W. Brown, P. K. Liaw and Z. Feng, “Texture variation and its influence on the tensile behavior of friction-stir processed magnesium alloy”, Scripta Mater., 54, 2006, pp.1859-1864.
19.M. Peel, A. Steuwer, M. Preuss, P. J. Withers, “ Microstructure, mechanical properties and residual stressesas a function of welding speed in aluminium AA5083 friction stir welds”, Acta Mater., 51 , 2003, pp.4791–4801.
20.Park SHC, Sato YS, Kokawa H. “Basal Plane Texture and Flow Pattern in Fricton Stir Weld of a Magnesium Alloy”, Metall. Mater Trans., A 2003. Vol.34A . pp.987.
21.K. N. Krishnan, “On the formation of onion rings in friction stir welds”, Mater. Sci. Eng., A327, 2002, pp.246-251.
22.M. W. Mahoney, C. G. Rhodes, J. C. Flintoff, R. A. Spurling and W. H. Bingel, “Properties of friction-stir-welded 7075 T651 aluminum”, Matall. Mater. Trans., 29A, 1998, pp.1955-1964
23.T. Obara, H. Yoshinga and S. Morozumi, “{1122}＜1123＞Slip System in Magsium”, Acta Metall., Vol.21, 1973, pp.845-853.
24.昌山正孝著、賴狄陽，『非鐵金屬材料』，復漢出版社，1993年1月，174頁。
25.C. R. Brooks, “Heat Treatment, Structure and Properties of Nonferrous Alloys”, ASM., 1982. pp.59-69.
26.S. S. Rao, “Mechanical Vibrations”, Addison-Wesley Publishing Company, Inc., 2nd ed., pp.4-160, 1990.
27.C. Y. Tang, M. Jie, W. Shen and K. C. Yung, “The Degradation of Elastic Proerties of Aluminum Alloy 2024T3 Due to Strain Damage, ” Scripta Metall. Mater., Vol.38, No.2, pp.221-238, 1998.
28.S. M. McGuire, M. E. Fine, O. Buck and J. D. Achenbach, “Nondestructive Detection of Fatigue Cracks in PM 304 Stainless Steel by Internal Friction and Elasticity”, J. Mater. Res., Vol.8, pp.2216-2223, 1993.
29.S. M. McGuire, M. E. Fine and J. D. Achenbach, “Crack Detection by Resonant Frequency Measurements”, Metal. Trans., A, Vol.26A, pp.1123-1127, 1995.
30.孫慶鴻、張啟軍、姚慧珠，『振動與噪音的阻尼控制』，機械工業出版社，北京，民國81年，38-57頁。
31.黃振賢，『機械材料』，新文京開發出版社，民國88年，436-444頁。
32.Sugimoto K, Niiya K, Okamoto T, Kishitake, “Study of Damping Capacity in Magnesium Alloys” K.Trans JIM., 1977, Vol18, no3, pp.277-288.
33.Srikanth N, Gaofeng CH, Gupta Manoj, “Enhanced damping of a magnesium alloy by addition of copper”M.J Alloy Compd., 2003, Vol.352, pp.106-110.
34.洪佳和，『亞共晶鋁-矽(-鎂)合金之共振破壞特性及其冶金影響因素之探討』，國立成功大學材料科學及工程學系，博士論文，民國90年。
35.李芳儀，『銅含量對Sn-Ag-Cu無鉛銲錫振動破壞特定之研究』，國立成功大學材料科學及工程學系，碩士論文，民國92年。
36.藍國峰，『Sn-Zn-xAg無鉛銲錫振動破壞特定之研究』，國立成功大學材料科學及工程學系，碩士論文，民國91年。
37.G. E. Dieter, “Mechanical Metallurgy”, 3rd ed., 1986, pp.243-249.