Kỷ yếu hội nghị khoa học công nghệ toàn quốc khí - Lần thứ IV THE APPLIED RESEARCH OF FRICTION WELDING TECHNIQUE IN NHA TRANG UNIVERSITY NGHIÊN CỨU ỨNG DỤNG KỸ THUẬT HÀN MA SÁT TẠI ĐẠI HỌC NHA TRANG Hưng Trà, 2bOkazaki Nha Trang University, Vietnam Nagaoka University of Technology, Japan a tra@ntu.edu.vn; bokazaki@mech.nagaokaut.ac.jp 1aTrần ABSTRACT In this paper, some new results in the friction welding research developed in Nha Trang University are presented The friction technique is quite suitable for joining alumunim alloys and superalloys This technique is recognized to be suitable for joining the unweldable metals and dissimilar joining The joints posses several preeminent points such as low distortion, low residual stress, free defects, and high strength Furthermore, this welding technique is a green technique, it is performed without gas and low energy Keywords: friction welding, aluminum alloys, superalloys, microstructure, strength TÓM TẮT Bài báo trình bày kết đạt nghiên cứu ứng dụng kỹ thuật hàn ma sát Đại học Nha Trang Kỹ thuật hàn ma sát cho thấy nhiều tính ưu việt, cho phép hàn hầu hết hợp kim nhôm siêu hợp kim dễ dàng, đặc biệt hàn hợp kim khó tính hàn hợp kim khác Chất lượng mối hàn đảm bảo không khuyết tật, biến dạng, ứng suất dư thấp độ bền cao Ngoài ra, công nghệ hàn xem công nghệ xanh, thân thiện với môi trường, không dùng gas chi phí lượng hàn thấp Từ khóa: hàn ma sát, hợp kim nhôm, siêu hợp kim, cấu trúc tế vi, độ bền INTRODUCTION Emerging as a high energy efficiency and versatility, friction welding (FW) has been found to be a key technique in metal joining This technique is suitable for all alloys including the alloys recognized to be unweldable by traditional fusion welding methods Currently, FW is being studied and applied in a wide range of applications in which the welding can be obtained with high strength and low distortion [1-7] Especial in the aerospace industry, where the high specific strength becomes a critical issue [5-7] The economic efficiency concerning to light structure is presented in Figure Even thought FW possesses several preeminent points, this technique is applied restrictively in Vietnam Only a few places address to this topic In order to develop this friction technique, we establish a Friction welding Laboratory in Nha Trang University Here, currently, several joints of alloys are fabricated by both friction welding technique and friction stir welding technique It is recognized that the joints are fabricated easily with free defects and high strength We hope, in the future, more and more connections between us and other researchers and/or manufacturers to develop this technique in Vietnam 414 Kỷ yếu hội nghị khoa học công nghệ toàn quốc khí - Lần thứ IV Figure 1: Money savings per pound of the lighter structure [8] RESEARCH METHODS AND MATERIALS The friction joints have been studied and fabricated by using the friction welding machine at Nha Trang Univiversity (denoted NTU FW machine) with the spindle power of 6.0 kW, vertical linear movement of 18.0 kN loading capacity and horizontal linear movement of 20.0 kN loading capacity In this work, two types of friction welding are applied in which one is friction stir welding and the other is rotated friction welding In the friction stir process, two aluminum alloy plates is welded by both similar and dissimilar alloys joining (fabricated for typical types of aluminum alloys: 5xxx, 6xxx, and 7xxx) In the rotation friction process, the joints of the high strength alloys is addressed RESULTS AND DISCUSSION 3.1 Friction stir processing Several types of welded joints are fabricated by the friction process In figure shows the friction stir welded joint of two AA5083 bars The tensile strength of the joint is obtained above 90% of that of base metal In Figure 3, the lap joints of two AA6061 plates are fabricated by the friction stir process The microstructure of the joint is polished and observed and it is found that the joint is defect free with the tensile strength of the joint reaches to above 75% of that of base metal In Figure 4, the lap joint of two AA7075 plates with thickness of 8.0 mm and length of 1200 mm are fabricated by the friction stir process The microstructure of the joint is polished and observed and it is found that the joint is defect free with the tensile strength of the joint reaches to above 77% of that of base metal In Figure shows the result of dissimilar joint between AA5083 and AA6061, the joint is free defects with tensile strength obtains above 73% of base metal AA6061 The dissimilar T-joint is also conducted on this FW machine This T-joint is fabricated between AA7075 and AA5083, Figure It is found that, the joint shows a good quality in both the macro and micro view The tensile strength of the joint is being investigated and will be opened soon The cross section microstructure of the FSW joint can be seen in Figure 7, where the joint is perfectly with free defects 415 Kỷ yếu hội nghị khoa học công nghệ toàn quốc khí - Lần thứ IV Figure 3: Friction stir welding of AA6061 plates by using NTU FW machine Figure 2: Friction stir welding of AA5083 bars by using NTU FW machine Figure 4: Friction stir welding of 7075 plates by using NTU FW machine (Welding length of 1.2 m) Figure 5: Dissimilar friction stir welding of AA5083 and AA6061 plates by using NTU FW machine Figure 6: Disimilar T-joint friction stir welding of AA5083 and AA7075 (Using NTU FW machine) 416 Kỷ yếu hội nghị khoa học công nghệ toàn quốc khí - Lần thứ IV Figure 7: Microstructure in cross section of FSW of AA6063 (a) region (i), (b) region (ii), (c) region (iii) and (d) base metal region 3.2 Rotated friction processing The dissimilar friction joint of two superalloys is fabricated This joint requires a large power and thus we conducted this work in Hitachi Co In this work, the superalloy Inconel 718 and Mar M247 are joined Here, the joint possesses a create quality with free defects and high strength, see figure 10 The tensile strength of the joint is equivalent to the base metals Further, the fatigue life of the joint is comparable to that of base metal [4] Figure 8: Cross section at the interface of the totation friction welding of superally Inconel 718 and Mar M247 (Fabricated in Hitachi Co.) 417 Kỷ yếu hội nghị khoa học công nghệ toàn quốc khí - Lần thứ IV CONCLUSIONS It is well known that aluminum alloys and superalloys as well are difficult to weld, especially in the dissimilar welding However, these alloys are fabricated successfully by the friction processing with free defects and high strength in Nha Trang University The friction technique promises several chances for not only joining alloys, but also for fabricating the composite components Further, this technique is possible for us to use in crack repair and local microstructure modifications REFERENCES [1] E D Nicholas, Friction processing technologies, Welding in The World 2003, 47(11/12), pp 2-9 [2] Tran Hung Tra, Desertation: Failure behaviors of the solid-state friction-welded joints under cyclic loadings at elevated temperatures, Nagaoka Univ of Tech., 2010 [3] Tran Hung Tra, M Okazaki, M Sakaguchi, K Suzuki, Fatigue crack propagation behavior of friction stir welding AA 6063-T5: Residual stress and microstructure effect, International Journal of Fatigue, 2012, Vol 43, pp 23-29 [4] Tran Hung Tra, Effect of weld parameters on the mechanical properties of friction stir welding AA6063-T5, ASEAN Engineering Journal, 2011, Vol 4, pp 73-81 [5] M Okazaki, M Sakaguchi, T H Tran, M Sekihara, Creep-fatigue and thermomechanical fatigue of friction-welded IN718/MarM247 dissimilar joint, Superalloys 2008, pp 221-228 [6] U Dressler, G Biallas, U Alfaro Mercado, Friction stir welding of titanium alloy TiAl6V4 to aluminium alloy AA2024-T3, Materials Science and Engineering A 2009, 256(1-2), pp 113-117 [7] F Daus, H Y Li, G Baxter, S Bray, P Bowen, Mechanical and microstructural assessments of RR1000 to IN718 inertia welds - effects of welding parameters, Mater Sci Tech 2007, 23(12), pp 1424-1432 [8] P F Mendez, T W Eagar, New trends in welding in the aeronautic industry: http://eagar.mit.edu/EagarPapers/Eagar192.pdf., 2006 AUTHOR’S INFORMATION Tran Hung Tra Nha Trang University Email: tra@ntu.edu.vn Phone: 0935272168 Okazaki, Nagaoka University of Technology, Email: okazaki@mech.nagaokaut.ac.jp 418