摩擦攪拌製程(Friction Stir Process, FSP)是一種表面改質的製程，可獲得再結晶之晶粒並改變鎂合金的織構。前人研究指出AZ系列鎂合金之拉伸性質受織構影響，且γ- Mg17Al12相對微觀組織及拉伸性質的影響甚大，故本研究利用FSP改質並進行後熱處理控制γ相之析出量，觀察顯微組織、微硬度與拉伸性質的改變，以釐清織構及γ相對AZ91的影響，並將AZ91-T4進行後熱處理以做為比對材。
　　實驗結果發現：試片經FSP改質後組織變化與固溶化熱處理相似。將FSP材及T4材施以175℃後熱處理後皆發現γ相的析出量與熱處理時間成正相關，且T4材的γ相析出量皆小於FSP材，可能是因為攪拌過程中導入應變能，利於後熱處理FSP材時γ相的成核成長。由XRD的結果顯示，FSP材織構較微弱而不明顯，HCP的底面約略沿著攪拌棒的凸梢圓周排列，但SZ區中央底面仍未垂直於拉伸方向，拉伸過程中可以啟動底面滑移系統；T4材的織構則與擠型材相同，底面平行於拉伸方向，拉伸過程中無法啟動底面滑移與拉伸雙晶。經175℃後熱處理後，FSP材在ND面之底面及{10(-1)1}面的峰值上升，PD面之{10(-1)1}面的峰值則下降；T4材的織構則變化不大。
　　後熱處理4h時，T4材延伸率無顯著的改變；FSP材則因α相生成拉伸雙晶，延伸率增加到約16%。後熱處理8h時，T4材因為晶粒大小較為均勻而使延伸率提升；FSP材α相生成的拉伸雙晶數較後熱處理4h之試片多，且發現裂縫生成，延伸率因γ相析出量增加而劣化。最後當時間達12h時，T4材延伸率可能因γ相而劣化；FSP材則發現α相的形變雙晶更多並發現裂縫，延伸率比後熱處理8h之試片差。由本實驗結果可知，同時兼具摩擦攪拌改質及γ相適量的析出量才能使後熱處理材獲得最佳延伸率。

The texture of magnesium alloys is changed and the grains would be well recrystallized by Friction Stir Process(FSP). Previous studies indicate the tensile properties of AZ serious magnesium alloys are affected by texture. Moreover, there are significant influences on microstructure and tensile properties by the γ-Mg17Al12. Therefore, I use post-heat treatment to control the precipitation of γ phase and observe the change of microstructure, micro-hardness, and tensile properties in order to investigate the effects of γ phase and texture on AZ91 magnesium alloys.
The variation of microstructure of AZ91-FSP is similar with AZ91-T4. The precipitation of γ phase is positive related with the time of post-heat treatment. Compared to AZ91-FSP, the γ phase precipitation of AZ91-T4 is fewer. Probably, the imported strain energy by FSP benefits the nucleation and growth of γ phase. By X-ray diffraction (XRD), the texture of AZ91-FSP is similar to the references. The results are in a texture which the basal plane normal is roughly surrounding the rotation pin surface, but not obviously. In the stir zone, the basal plane is not perpendicular to the tensile direction. As the result, the basal plane slip systems of AZ91-FSP are activated during the tensile test. The texture of AZ91-T4 is identical to extrusions, which means the basal plane is parallel to the tensile direction. The basal plane slip systems and tensile twinning of AZ91-FSP are not activated during the tensile test. After AZ91-FSP are post-heat treated at 175℃, the peak of basal plane and {10(-1)1} plane increase along the ND; the peak of {10(-1)1} plane decreases along the PD.
The elongation of T4 + T6-4h has no notable change; the elongation of FSP-ph4 increase to about 16% because of tensile twinning of α phase. T4 + T6-8h have better elongation result from uniform grain size; despite of more tensile twinning of α phase, the elongation of FSP-ph8 is worse result from the much more γ precipitation, and there are tensile cracks. The elongation of T4 + T6-12h is worse probably because of the γ precipitation and tensile cracks; the elongation of FSP-ph12 is worse than FSP-ph8. Based on the experimental results, we can acquire the best elongation by both of FSP and appropriate γ precipitation.

1.I.J.Polmear, “Magnesium Alloys and Applications” , Mater. Sci. Technol., Vol.10(1), 1994, pp.1-15.
2.劉柏志，『7075與A356鋁合金異質摩擦攪拌銲接後之微觀組織及拉伸性質研究』，國立成功大學材料科學及工程學系研究所碩士論文，民國98年。
3.W. Woo, H. Choo, D. W. Brown, P. K. Liaw, Z. Feng, “Texture variation and its influence on the tensile behavior of friction-stir processed magnesium alloy”, Scripta Mater., Vol.54, 2006, pp.1859-1864.
4.蔡原宗，『摩擦攪拌AZ61鎂合金於200℃~250℃拉伸性質及動態再結晶之應變速率效應研究』，國立成功大學材料科學及工程學系研究所碩士論文，民國97年。
5.莊凱傑，『摩擦攪拌製程對AZ31鎂合金拉伸及振動破壞特性影響之研究』，國立成功大學材料科學及工程學系研究所碩士論文，民國96年。
6.Y. Tamura, Y.Kida, H. Tamehiro, N. Kono, H. Soda, A. McLean, “The effect of manganese on the precipitation of Mg17Al12 phase in magnesium alloy AZ91”, J. Mater. Sci., Vol.43, 2008, pp.1249-1258.
7.Yongbing Li, Yunbo Chen, Hua Cui, Baiqing Xiong, Jishan Zhang, “Microstructure and mechanical properties of spray-formed AZ91 magnesium alloy”, Mater. Characterization, Vol.60, 2009, pp.240-245.
8.Zhifeng Li, Jie Dong, Xiao Qing Zeng, Chen Lu, Weng Jiang Ding, “Influence of Mg17Al12 intermetallic compounds on the hot extruded microstructures and mechanical properties of Mg-9Al-1Zn alloy” , Mater. Scie. And Eng., A466, 2007, pp.134-139.
9.M. M. Avedesian and H. Baker, ASM Specialty Handbook, “Magnesium and Magnesium Alloys”, 1999, pp.13-43.
10.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。
11.M. M. Avedesian and H. Baker, “ASM Metals Handbook-Metallography, Structures and Phase Diagrams”, Vol.8, 1973, p.398.
12.O. Lunder, T. Kr. Aune, K. Nisancioglu, “Effect of Mn Additions on the Corrosion Behavior of Mould-Cast Magnesium ASTM AZ91”, Corrosion, 43, 5, 1987, p.291.
13.Michael M. Avedesian and Noranda Magnesium Inc., ASM Specialty Handbook, “Magnesium and Magnesium Alloys”, Materials Information Society, 1999, pp.14-15.
14.A. Srinivasan, J. Swaminathan, U. T. S. Phillai, Krishna Guguloth, B. C. Pai, “Effect of combined addition of Si and Sb on the microstructure and creep properties of AZ91 magnesium alloy”, Mater. Scie. And Eng., A485, 2008, pp.86-91.
15.M. M. Avedesian and H. Baker, “Magnesium and Magnesium Alloys”, ASM Int., 1999, pp.13-21.
16.W. M. Thomas, E. D. Nicholas, J. C. Needham, M. G. Murch, P. Temple Smith and C. J. Dawes, “Friction stir butt welding”, International Patent Application, No.PCT/GB92/02203 and GB Patent Application, No. 9125978. 8, 1991.
17.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.
18.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.
19.Z. Y. Ma, R. S. Mishra, M. W. Mahoney, “Superplastic Deformation Behavior of Friction Stir Processed 7075 Al Alloy”, Acta Mater., Vol.50, 2002, pp.4419-4430.
20.Uday Chakkingal, Arief B. Suriadi, 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.
21.S. Benavifes, Y. Li, L. E. Murr, “Ultrafine Grained Materials”, TMS. Warrendale. PA., 2000, pp.155.
22.昌山正孝著、賴狄陽譯，『非鐵金屬材料』，復漢出版社，1993年1月，174頁。
23.『鎂合金創新應用與摩擦攪拌銲接技術研討會講義』，台灣鎂合金協會，民國97年12月，4頁。
24.R. Reed-Hill and R. Abbaschian, “Physical Metallurgy Principles 3rd Edition”, PWS Publishing Company, United States of America, 2004, pp.5-18~5-21.
25.S.R. Agnew, J.A. Horton, M.H. Yoo, “Transmission Electron Microscopy Investigation Investigation of 〈c+a〉Dislocation in Mg and α-Solid Solution Mg-Li Alloys”, Metall. Mater Trans., Vol.33A, 2002, pp.851-858.
26.A. H. Feng and Z. Y. Ma, “Enhanced mechanical properties of Mg-Al-Zn cast alloy via friction stir processing”, Scripta Mater., Vol.56, 2007, pp.397-400.
27.W. Woo, H. Choo, D. W. Brown, P. K. Liaw, Z. Feng, “Texture variation and its influence on the tensile behavior of a friction-stir processed magnesium alloy”, Scripta Mater., Vol.54, 2006, pp.1859-1864.
28.『鎂合金創新應用與摩擦攪拌銲接技術研討會講義』，台灣鎂合金協會，民國97年12月，14頁。
29.Y. N. Wang, C. I. Chang, C. J. Lee, H. K. Lin, J. C. Huang, “Texture and weak grain size dependence in friction stir processed Mg-Al-Zn alloy”, Scrip. Mater., Vol.55, 2006, pp.637-640.
30.B. M. Darras, M. K. Khraisheh, F. K. Abu-Farha, M. A. Omar, “Friction stir processing of commercial AZ31 magnesium alloy”, Journal of Mater. Processing Technology, Vol.191, 2007, pp.77-81.
31.Guohua Wu, “The effect of Ca and rare earth elements on the microstructure and mechanical properties and corrosion behavior of AZ91D”, Materials Science and Engineering A, 408, 2005, pp. 255-263.