本研究分別選用AA7075-T6、AA7075-O、Gr.2 Ti，三種材料，對AA7075-O進行熱處理、FSW(800 rpm搭配50 mm/min)、銲後熱處理；對AA7075-T6 進行單雙面FSW(600 rpm搭配60 mm/min) 、銲後熱處理；對AA7075-T6與Gr.2 Ti 進行FSW(600 rpm搭配40 mm/min)，對其上三種不同組合所達成的銲接條件進行機械性質與微觀組織的分析與探討。
在AA7075-T6材的研究顯示，雙面銲接由於多一道銲接過程，更多的熱量提供使其在機械性質表現上較單面銲接降低，但在銲後熱處理後，其拉伸性質則較單面銲接增加，二者在銲道皆面臨AGG異常晶粒生長的狀況，經熱處理後產生脆性斷裂的問題。在AA7075-O材的研究結果顯示，熱處理時時效溫度越高會導致材料特性抵達峰值時間越少，但其峰值表現也會越低。AA7075-O在銲接後，於其銲道有晶粒細化的表現，因此該區域硬度獲得提升，但在愈遠離銲道則愈發降低，直至母材強度。經銲後熱處理後，若要成功獲得優良的機械性質，必須避免銲道裂縫與AGG的產生，經銲後熱處理之試片與母材熱處理後之機械性質趨勢一致，皆能達成約母材熱處理的80%強度，並且在與T6材FSW的銲接性質比較中，更為提升。而其中AA7075-O在進行銲後與固溶淬火後的拉伸試驗中，可以發現有DSA的產生，能為其增加強度。在AA7075-T6與Gr.2 Ti 異質銲接的研究結果顯示，在600 rpm搭配40 mm/min可以達到無缺陷接合，從EPMA的觀察中可以發現，僅0.1 mm的偏置距離已讓鈦和鋁合金在攪拌區形成化合物及鈦碎屑的攪拌，而IMC層由於其硬脆的特性，導致拉伸試驗皆斷裂於該處。

This research explored three different materials: AA7075-T6, AA7075-O, and Gr.2 Ti, using various welding and post-welding heat treatment processes. For AA7075-O, the processes included heat treatment, Friction Stir Welding (FSW), and post-weld heat treatment. For AA7075-T6, single and double-sided FSW and post-weld heat treatment were performed. Lastly, FSW was conducted between AA7075-T6 and Gr.2 Ti, and the mechanical properties and microstructure of these three combinations were analyzed and discussed.
In the investigation of AA7075-T6, double-sided welding showed slightly inferior mechanical properties compared to single-sided welding due to the additional welding process and higher heat input. However, post-weld heat treatment improved its tensile properties, showing slightly higher performance than single-sided welding. Both welds faced the issue of abnormal grain growth (AGG) in the weld zone, which, if not avoided, could lead to brittle fracture after heat treatment.
For AA7075-O, the research showed that higher aging temperatures during heat treatment caused the material's characteristics to peak earlier but at lower levels, and vice versa. The welded zone exhibited grain refinement, resulting in increased hardness in that area, while the hardness decreased as one moved further away from the weld zone, eventually reaching the base material's strength. After post-weld heat treatment, obtaining excellent mechanical properties required avoiding weld cracking and AGG. The mechanical properties of the samples treated with post-weld heat treatment aligned with the trend of the base material after heat treatment, achieving approximately 80% of the base material's strength. Moreover, the properties compared to FSW welding with AA7075-T6 improved.
Regarding the dissimilar welding of AA7075-T6 and Gr.2 Ti, EPMA observations revealed that even a small offset distance of 0.1 mm resulted in the formation of compounds and titanium debris in the stirring zone between titanium and aluminum alloys. The presence of an IMC (Intermetallic Compound) layer led to fracture in tensile tests due to its brittle nature.

[1] E. Ezugwu, Z. Wang, " Titanium alloys and their machinability—a review", Journal of materials processing technology, Vol. 68(3), 1997, pp. 262-274.
[2] M. Tajally, E. Emadoddin, " Mechanical and anisotropic behaviors of 7075 aluminum alloy sheets", Materials & Design, Vol. 32(3), 2011, pp. 1594-1599.
[3] T. Dursun, C. Soutis, " Recent developments in advanced aircraft aluminium alloys", Materials & Design Vol. 56, 2014, pp. 862-871.
[4] Z. Ma, C. Wang, H. Yu, J. Yan, H. Shen, " The microstructure and mechanical properties of fluxless gas tungsten arc welding–brazing joints made between titanium and aluminum alloys", Materials & Design, Vol. 45, 2013, pp. 72-79.
[5] S. Chen, L. Li, Y. Chen, J. Huang, " Joining mechanism of Ti/Al dissimilar alloys during laser welding-brazing process", Journal of Alloys and Compounds, Vol. 509(3), 2011, pp. 891-898.
[6] X. He, F. Gu, A. Ball, " A review of numerical analysis of friction stir welding", Progress in Materials Science, Vol. 65, 2014, pp. 1-66.
[7] 鄭元愷，" AA7075鋁合金與Ti-6Al-4V合金摩擦攪拌銲接微觀組織與機械性質研究"， 國立臺灣師範大學碩士論文， 2021年。
[8] R. Biradar, S. Patil, " A review of tensile, hardness, wear, and microstructural characteristics of friction stir welded/processed composites", Materials Today: Proceedings, Vol. 82, 2023, pp. 8-13.
[9] S.N. Kumar, T. Shashank, Dhruthi, " Different Ceramic Reinforcements In Aluminium Metal Matrix Composites", Ecs Journal Of Solid State Science And Technology, Vol. 10(5), 2021.
[10] R.W. Revie, " Uhlig's corrosion handbook", John Wiley & Sons, 2011.
[11] 郭承典，" 純鈦與6061鋁合金摩擦攪拌異質接合之機械性質與抗腐蝕特性研究"， 國立臺灣師範大學碩士論文， 2019年。
[12] TheAluminumAssociation," Industry Standards", 2021, https://www.aluminum.org/industry-standards.
[13] 黃振賢，" 金屬熱處理"，16刷 ， 文京圖書有限公司， 1985。
[14] W.W. Wang, B.B. Jia, S.J. Luo, " Effect of heat treatment on mechanical properties of thixoformed 7A09 aluminum alloy", Transactions of Nonferrous Metals Society of China, Vol. 19, 2009, pp. s337-s342.
[15] M. Nandana, K.U. Bhat, C. Manjunatha, " Effect of retrogression and re-ageing heat treatment on microstructure and microhardness of aluminium 7010 alloy", MATEC Web of Conferences, EDP Sciences, 2018, pp. 102-103.
[16] N.M. Siddesh Kumar, Dhruthi, G.K. Pramod, P. Samrat, M. Sadashiva, " A Critical Review on Heat Treatment of Aluminium Alloys", Materials Today: Proceedings, Vol. 58, 2022, pp. 71-79.
[17] M.B. Lezaack, A. Simar, " Avoiding abnormal grain growth in thick 7XXX aluminium alloy friction stir welds during T6 post heat treatments", Materials Science and Engineering: A, Vol. 807, 2021, p. 140901.
[18] I. Charit, R.S. Mishra, " Abnormal grain growth in friction stir processed alloys", Scripta Materialia, Vol. 58(5), 2008, pp. 367-371.
[19] 台灣輕金屬協會，" 鈦-特性及應用"， 2022， https://www.twlma.org.tw/Profile/Detail?id=17。
[20] H.K.D.H. Bhadeshia," Metallurgy of Titanium and its Alloys", 2006, http://www.phase-trans.msm.cam.ac.uk/2003/titanium.movies/titanium.html.
[21] C. Veiga, J. Davim, A. Loureiro, " Properties and applications of titanium alloys: a brief review", Rev. Adv. Mater. Sci, Vol. 32(2), 2012, pp. 133-148.
[22] A. Karpagaraj, N. Siva shanmugam, K. Sankaranarayanasamy, " Some studies on mechanical properties and microstructural characterization of automated TIG welding of thin commercially pure titanium sheets", Materials Science and Engineering A, Vol. 640, 2015, pp. 180-189.
[23] J. Niagaj, " Peculiarities of A-TIG welding of titanium and its alloys", Archives of Metallurgy and Materials, Vol. 57(1), 2012, pp. 39-44.
[24] T. Chai, C.K. Chou, " Mechanical properties of laser-welded cast titanium joints under different conditions", Journal of Prosthetic Dentistry, Vol. 79(4), 1998, pp. 477-483.
[25] H. Liu, K. Nakata, N. Yamamoto, J. Liao, " Mechanical properties and strengthening mechanisms in laser beam welds of pure titanium", Science and Technology of Welding and Joining, Vol. 16(7), 2011, pp. 581-585.
[26] V. Dhinakaran, S.V. Shriragav, Y.F.A. Fathima, M. Ravichandran, " A review on the categorization of the welding process of pure titanium and its characterization", Materials Today: Proceedings, Vol. 27, 2020, pp. 742-747.
[27] W.B. Lee, C.Y. Lee, W.S. Chang, Y.M. Yeon, S.B. Jung, " Microstructural investigation of friction stir welded pure titanium", Materials Letters, Vol. 59(26), 2005, pp. 3315-3318.
[28] W. Thomas, " Friction Stir Butt Welding, International Patent Application No. PCT/GB92", GB Patent Application No. 9125978.8, Vol. 1, 1991.
[29] 張志溢，黃志青，" 摩擦旋轉攪拌製程之新近發展與應用"， 科儀新知 ， 139卷 ， 2004， 第59-73頁 。
[30] F. Gemme, Y. Verreman, L. Dubourg, M. Jahazi, " Numerical analysis of the dwell phase in friction stir welding and comparison with experimental data", Materials Science and Engineering A, Vol. 527(16-17), 2010, pp. 4152-4160.
[31] R.S. Mishra, Z. Ma, " Friction stir welding and processing", Materials science and engineering: R: reports, Vol. 50(1-2), 2005, pp. 1-78.
[32] J. Cho, Hyung, D.E. Boyce, P.R. Dawson, " Modeling strain hardening and texture evolution in friction stir welding of stainless steel", Materials Science and Engineering: A, Vol. 398(1-2), 2005, pp. 146-163.
[33] H. Liu, H. Fujii, M. Maeda, K. Nogi, " Tensile properties and fracture locations of friction-stir welded joints of 6061-T6 aluminum alloy", Journal of materials science letters, Vol. 22, 2003, pp. 1061-1063.
[34] M.B. Bever, D.L. Holt, A.L. Titchener, " The stored energy of cold work", Progress in materials science, Vol. 17, 1973, pp. 5-177.
[35] L. Fratini, G. Buffa, " CDRX modelling in friction stir welding of aluminium alloys", International Journal of Machine Tools and Manufacture, Vol. 45(10), 2005, pp. 1188-1194.
[36] S. Naik, S. Panda, S. Padhye, G. Lobo, G. Joshi, S. Deshmukh, A. Ingle, " Parametric review on friction stir welding for under water and dissimilar metal joining applications", Materials Today: Proceedings, 2021, pp. 3117-3122.
[37] A. Simar, F. Avettand, N. Marie, " State of the art about dissimilar metal friction stir welding", Science and Technology of Welding and Joining, Vol. 22(5), 2017, pp. 389-403.
[38] S. Shankar, K.P. Mehta, S. Chattopadhyaya, P. Vilaça, " Dissimilar friction stir welding of Al to non-Al metallic materials: An overview", Materials Chemistry and Physics, Vol. 288, 2022, p. 126371.
[39] B. Li, Z. Zhang, Y. Shen, W. Hu, L. Luo, " Dissimilar friction stir welding of Ti–6Al–4V alloy and aluminum alloy employing a modified butt joint configuration: Influences of process variables on the weld interfaces and tensile properties", Materials & Design, Vol. 53, 2014, pp. 838-848.
[40] A. Kar, S.K. Choudhury, S. Suwas, S.V. Kailas, " Effect of niobium interlayer in dissimilar friction stir welding of aluminum to titanium", Materials Characterization, Vol. 145, 2018, pp. 402-412.
[41] A. Kar, S. Suwas, S.V. Kailas, " Two-pass friction stir welding of aluminum alloy to titanium alloy: a simultaneous improvement in mechanical properties", Materials Science and Engineering: A, Vol. 733, 2018, pp. 199-210.
[42] A. Wu, Z. Song, K. Nakata, J. Liao, L. Zhou, " Interface and properties of the friction stir welded joints of titanium alloy Ti6Al4V with aluminum alloy 6061", Materials & Design, Vol. 71, 2015, pp. 85-92.
[43] U. Dressler, G. Biallas, U.A. Mercado, " Friction stir welding of titanium alloy TiAl6V4 to aluminium alloy AA2024-T3", Materials Science and Engineering: A, Vol. 526(1-2), 2009, pp. 113-117.
[44] M.J. Starink, " Effect of compositional variations on characteristics of coarse intermetallic particles in overaged 7000 aluminium alloys", Materials Science and Technology, Vol. 17(11), 2001, pp. 1324-1328.
[45] P. Cavaliere, A. Squillace, " High temperature deformation of friction stir processed 7075 aluminium alloy", Materials Characterization, Vol. 55(2), 2005, pp. 136-142.
[46] X. Xu, Y. Zhao, X. Wang, Y. Zhang, Y. Ning, " The rapid age strengthening induced by Ag additions in 7075 aluminum alloy", Materials Science and Engineering: A, Vol. 648, 2015, pp. 367-370.
[47] B.S. Gong, Z.J. Zhang, J.P. Hou, R.H. Li, R. Liu, Q.Q. Duan, X.G. Wang, H.Z. Liu, F.G. Cong, G. Purcek, H. Yanar, M. Demirtas, Z.F. Zhang, " Investigation on the fatigue behavior of 7075 aluminum alloy at different aging states", International Journal of Fatigue, Vol. 175, 2023, p. 107817.
[48] P.V. Kumar, G.M. Reddy, K.S. Rao, " Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment", Defence Technology, Vol. 11(4), 2015, pp. 362-369.
[49] S.V. Sajadifar, G. Moeini, E. Scharifi, C. Lauhoff, S. Böhm, T. Niendorf, " On the Effect of Quenching on Postweld Heat Treatment of Friction-Stir-Welded Aluminum 7075 Alloy", Journal of Materials Engineering and Performance, Vol. 28(8), 2019, pp. 5255-5265.
[50] G. Sadeghi, Mojtaba, A. Kasiri, Masoud, K. Amini, " Friction stir welding of dissimilar joints between commercially pure titanium alloy and 7075 aluminium alloy", Transactions of FAMENA, Vol. 41(1), 2017, pp. 81-90.
[51] I. Peter, M. Rosso, " Study of 7075 Aluminium Alloy Joints", Scientific Bulletin of'Valahia'University. Materials & Mechanics, Vol. 15(13), 2017.
[52] P. Zhou, Y. Song, L. Hua, J. Lu, J. Zhang, F. Wang, " Mechanical behavior and deformation mechanism of 7075 aluminum alloy under solution induced dynamic strain aging", Materials Science and Engineering: A, Vol. 759, 2019, pp. 498-505.
[53] K. Ishida, Y. Gao, K. Nagatsuka, M. Takahashi, K. Nakata, " Microstructures and mechanical properties of friction stir welded lap joints of commercially pure titanium and 304 stainless steel", Journal of Alloys and Compounds, Vol. 630, 2015, pp. 172-177.
[54] I. Kalemba-Rec, M. Wróbel, M. Kopyściański, " Investigations of friction stir welds between 5083 and 7075 aluminum alloys using EBSD and X-Ray techniques", Acta Physica Polonica A, Vol. 130(4), 2016, pp. 996-999.