本論文以2024鋁合金為研究對象，分兩部分進行研究：
一部分為2024鋁合金熱裂性研究，以惰氣鎢極電弧銲(TIG)，在不使用填料情況下，利用點可調式應變試驗(Spot Varestraint Test)，探討外加應變量及熱循環次數對2024-T351及2024-T6熱裂敏感性之影響。經由光學顯微鏡與掃瞄電子顯微鏡觀察，探討微觀組織。研究結果顯示：2024-T351、2024-T6經多重熱循環後熔融區熱裂敏感性並無明顯之影響，但對熱影響區的金屬熱影響區(W. M. HAZ)兩種鋁合金卻都有顯著之影響，隨著熱循環次數的增加，在金屬熱影響區之熱裂縫會有明顯的成長，另母材熱影響區(B. M. HAZ)之熱裂縫2024-T351也隨著熱循環次數的增加而增加，而2024-T6則無此現象。另外隨著外加應變量之增加，兩種材料之裂縫總長度(Total Crack Length, TCL)並無增加，但在最大裂縫長度(Maximum Crack Length, MCL)上，2024-T351鋁合金熔融區之最大裂縫長度會隨著熱循環次數之增加而加大，而2024-T6鋁合金並無明顯現象。由金相顯微組織圖可知，熱裂縫發生的位置在熔融區與熱影響區，很明顯的的裂縫均沿著晶粒邊界發生。再經由SEM觀察分析，兩種鋁合金材料皆呈現熔融區為凝固熱裂及熱影響區為液化熱裂的形式。
第二部分為2024鋁合金與7050鋁合金做異質銲接後，探討其銲後之微觀結構與機械性質。銲接採惰氣鎢極電弧銲並分別添加A2319與A5356填料進行對接銲。銲後再施以自然時效(T1)與固溶時效(T4)熱處理，實驗結果顯示: (1) 2024、7050異質接合後經固溶處理(T4)，熔融區之微硬度值較自然時效(T1)大幅地提升約20-30Hv (2) 2024、7050異質接合後，採ER2319較ER5356填料在T1處理後有較高的極限抗拉強度(UTS)、降伏強度(YS)與伸長率(El)，但經固溶處理(T4)後，其極限抗拉強度(UTS)、降伏強度(YS)則差異不大。

The main purpose of this study focuses on 2024 aluminum alloys. it includes two parts:
The first part aims to investigate the hot cracking susceptibility of 2024 aluminum alloys. The specimens were experimented with tungsten Inert gas welding (TIG) at first under the condition of no filler metal used. Then, the spot varestraint testing was used to evaluate the effect resulting from the times of thermal cycles and augment strain over hot cracking susceptibility of 2024-T351 and 2024-T6 aluminum alloys. Meanwhile, the causes and patterns of hot cracking were observed and analyzed with Metallographic test and scanning electron microscope (SEM). The experimental result shows that the times of thermal cycles is irrelevant to hot cracking susceptibility in the weld fusion zone of 2024-T351 and 2024-T6. But the times of thermal cycles does affect hot cracking susceptibility in weld metal heat affected zone (W. M. HAZ) of both 2024-T351 and 2024-T6. As the times of thermal cycles increases, the length of hot cracks grows. Besides, the length of hot cracks in base metal heat affected zone (B. M. HAZ) of 2024-T351. However, this phenomenon does not appear in base metal heat affected zone (B. M. HAZ) of 2024-T6.on the other hand, as augment strain given increases, the total crack length (TCL) of these two materials both remains constant. With Metallographic test, the hot cracking occurrence was seen lying along the crystalline grain boundary in fusion zone and HAZ. Hot cracks yielded in fusion zone and in HAZ are categorized to solidification cracking and liquation one respectively. The types of hot cracking can be further identified with SEM.
The second part focuses on the research over mechanical property of dissimilar metal welding with 2024-T351 and 7050-T7451 through metallography and tensile test. TIG was adopted. ER2319 and ER5356 serve as individual filler during welding. After welding, specimens were conducted with respectively different heat treatment, natural aging treatment (T1) and solution heat treatment (T4). The experimental result indicates: (1)The micro-hardness in fusion zone of dissimilar metal welding enormously after T4 is enormously bigger than that after T1. The difference can achieve 20 to 30 Hv. (2) The specimens using ER2319 as filler have higher ultimate tensile strength (UTS), yield strength (YS) and elongation (El) than those using ER5356 after T1. But the above-mentioned parameters of specimens with these two fillers show no difference after T4.

1.G. E. Totten and D. S. MacKenzie, “Handbook of aluminum”, Marcel Dekker, 2003.
2.黃錦鐘，鋁合金的銲接(一)-鋁合金的種類與基本知識，機械月刊，第22卷，第7期，1996。
3.劉文海，鋁合金新材料的方展動向，機械工業雜誌，第291期，2007。
4.J.E. Hatch, Editor, Aluminum: Properties and Physical Metallurgy, ASM, Metals Park, Ohio 1984.
5.Welding Technology Institute of Australia：Aluminothermic Weld Defects, 2006.
6.T. Y. Lim, M. M. Ratnam and M. A. Khalid, Automatic classification of weld defects using simulated data and an MLP neural network, Vol 49, pp. 154-159, 2007.
7.L. Baughurst and G. Voznaks, Welding defects, causes and correction, Aspec Engineering, 2009.
8.E.A. Starke, Jr. and J.T. Staley, Application of modern aluminum alloys to aircraft, Prog. Aerospace Sci, Vol.32 , pp. 131-172, 1996.
9.黃振賢，機械材料，台北：文京圖書公司， pp.311-327, 1990。
10.J. R. Davis, ASM Specialty Handbook : Aluminum and Aluminum Alloys, ASM International, 1993.
11.盧仲湘，高強度鋁合金之銲接熱裂研究，國立交通大學機械工程研究所，碩士論文，1989。
12.鄭慶民，熱處理型鋁合金銲接性之研究，國立交通大學機械工程研究所，博士論文，2005。
13.黃振賢，金屬熱處理，台北：文京圖書公司，1993。
14.陳俊凱，鋁合金6061與7075之銲接熱裂研究，國立台灣師範大學工業教育學系碩士論文，2003。
15.C. H. Gür and I. Yildiz, "Determining the impact toughness of age-hardened 2024 al-alloy by nondestructive measurements.
16.K. Sindo. Welding metallurgy. NewYork: John Wiley ＆ Sons. 1987.
17.I.J. Polmear, Aluminium Alloys – A Century of Age Hardening, Materials forum Vol.28, 2004.
18.田潮訓，航空用鋁-銅系合金摩擦攪拌接合，國立台灣師範大學工業教育學 系碩士論文，2005。
19.姜志華，鋁合金電弧銲接及硬軟銲應用技術，台北：徐氏基金會，1995。
20.ASM, Metals Handbook. 9th Ed, Vo1.14, heat treament of aluminum alloys, pp.675-718, 1985.
21.周長彬、蘇程裕、蔡丕椿、郭央諶 編著，銲接學，全華圖書股份有限公司，2007。
22.楊智綱，高強度航空用7000系鋁合金機械性質、抗應力腐蝕破壞性及銲接熱影響區特性之研究，國立中央大學機械工程研究所博士論文，2001。
23.W.A.Baselack, J.C.Lippold and W.F.Savage, Unmixed Zone Formation in Austenitic Stainless Steel Weldments, Welding Journal, Vol.58, No.6, pp.169, 1979.
24.ASM.Aluminum Alloy Castings: Properties, Processes and Applications, pp. 47-54, 2005.
25.姜志華編著，鋁合金電弧銲接及硬軟銲應用技術，徐氏基金會出版。
26.黃錦鐘，鋁合金的銲接(四)-銲接缺陷的種類及其對策，機械月刊，第22卷，第10期，1996。
27.黃錦鐘，鋁合金的銲接(五)-銲接變形、銲接裂縫及氣孔，機械月刊，第22卷，第12期，1996。
28.T. Anderson, How to Avoid Cracking in Aluminum Alloys, Welding Journal, pp.25-27, 2005.
29.洪偉仁，鋁合金和到熱裂，銲接與切割，第2卷，第1期，1993。
30.C. Huang and S. KOU, Liquation Cracking in Full- Penetration Al-Cu Welds, Welding Journal, pp.50-58, 2004.
31.R. P. LIU, Z. J. DONG,Y. M. PAN, Solidification crack susceptibility of aluminum alloy weld metals, Trans.Nonferrous Met. SOC. China 16, pp.110-116, 2006.
32.Kazutoshi Nishimoto, Recent Topics of Welding Metallurgy Relating to Hot Cracking and Embrittlement in Iron and Nickel-base Alloys, Lab, Material Joining Process, Department of Manufacturing Science Graduate School of Engineering Osaka University, 2005.
33.V. Shankar, T.P.S. Gill, S.L. Mannan and S. Sundaresan,
Solidification Cracking in Austenitic Stainless Steel Welds, Sadhana, Academy Proceedings in Engineering Sciences Vol.28, pp.359-382, 2003.
34.鐘福見，如何避免鋁合金銲接龜裂，銲接與切割，第16卷，第2期，2006。
35.H.Herser, Value of Different Hot Cracking Tests for the Manufacturer of Filler Metals. Hot cracking phenomena in welds. Springer Berlin Heidelberg, pp. 305-327, 2005.
36.朱登雄譯，銲接龜裂與其防止對策(2)-高溫龜裂，機械月刊，第10期，pp.122-126，1989。
37.郭飛虎，「2024, 2219及6061高強度鋁合金的銲接性研究」，銲接與切割，第6 卷第2 期，1996。
38.M. Shibahara, H. Serizawa and H. Murakawa, Finite Element Analysis for Hot Cracking on Transverse Cross Section Using Temperature Dependent Interface Element and Quantification of Parameters Included in Proposed Method, Quarterly Journal of The Japan Welding Society, pp.94-100, 2004.
39.Sindo Kou, Solidifi cation and Liquation Cracking Issues in Welding, Welding Journal, pp.37-42, 2003.
40.N. Coniglio, C. E. Cross, T. Michael, And M. Lammers, Defining a Critical Weld Dilution to Avoid Solidification Cracking in Aluminum, Welding Journal, Welding Journal, Vol.87 pp.237-247, 2008.
41.N. Coniglio, 2008. Aluminum alloy weldability: Identification of weld solidification cracking mechanisms through novel experimental technique and model development. Ottovon- Guericke University, 2008.
42.W. F. Savage, and C. D. Lundin, idid 44: 443, 1965.
43.林后堯、鄭慶民、周長彬，多功能可調應變試驗機之發展及其應用研究，中華民國焊接協會91年度焊接論文發表會，2002。
44.黃錦鐘，鋁合金的銲接(二)-各種銲接的原理與特徵，機械月刊，第22卷，第8期，1996。
45.A. D. Althouse, C. H. Turnquist, W. A. Bowditch, Modern Welding, Goodheart-Willcox Co., Inc. 1976, chap. 11-12.
46.朱健松、劉育廷，銲接參數對氣體金屬電弧銲接特性之研究，農業機械學刊，第14卷，第3期，2005。
47.Metal Handbook, ASM Ninth Edition, V4, "Heat Treatment", pp.675-718.
48.A. Gutierrez, J.C. Lippold, W. Lin, Mater. Sci. Forum 217-222, pp. 1691-1696, 1996.