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International Journal of Latest Trends in Engineering and Technology Vol.(8)Issue(3), pp.121-126 DOI: http://dx.doi.org/10.21172/1.83.015 e-ISSN:2278-621X EFFECT OF TOOL PIN PROFILE ON DISSIMILAR FRICTION STIR WELDING OF ALUMINUM ALLOY AA 7075 T651 AND AA 6061 T6 H.M.Anil Kumar1 and Dr.V.Venkata Ramana 2 Abstract- Friction stir welding is a solid state welding process where in two materials are joined without melting the material. The process is well suited for non ferrous materials such as aluminum, copper, magnesium, zinc etc. It is an effective technique for joining dissimilar metal and alloys and finds its application in various fields such as aerospace and automotive industries. In this attempt is made to join aluminum alloy AA 7075 T651 and AA 6061 T6 condition by friction stir welding technique under different process parameters such as tool rotation speed (750 rpm to 1250 rpm), welding speed (90 mm/min to 110 min) and using five different tools pin profiles –threaded cylindrical (TC), triangular profile (TP), conical profile (CP), square profile (SP) and hexagonal profile (HP). The outcome of the experimentation indicated that square tool pin profile and hexagonal tool pin profile at the tool rotation speed of 1250 rpm and the welding speed of 110 mm/min respectively yielded good quality welds in contrast to other tool pin profiles. Keywords – Dissimilar Friction stir welding, tool pin profile, tensile strength, microstructure I. INTRODUCTION Friction stir welding (FSW) is a solid state joining process developed at The Welding Institute (TWI), Cambridge, UK, in 1991. The process uses rotating tool which provides frictional heat and mixing to produce a weld between two metallic surfaces below their melting point. Since the process works below the melting point of the metals some of the defects like cracks, porosity and blow holes arising out of fusion welding process are eliminated. Koilraj et al  investigated the optimum values of dissimilar friction stir welding process parameters such as tool rotational speed, transverse speed, tool geometry and ratio between tool shoulder diameter and pin diameter for aluminium AA2219T87 and AA5083-H321 alloy. The results indicated that optimum levels of the rotational speed, transverse speed, and D/d ratio are 700 rpm, 15 mm/min and 3 respectively. The cylindrical threaded pin tool profile was found to be the best in contrast to other profiles. The D/d ratio contributes 60% to the satisfactory welds.Govind Reddy et al  optimized the process parameters on the work on dissimilar frictions stir welding using AA2024-AA7075 aluminum alloy. In this work effect of tool rotation speed and welding speed on the tensile strength is investigated by developing mathematical model using response surface methodology and Nelder Mead algorithm.R Palanivel et al  studied the effects of tool rotational speed and pin profile on microstructure and tensile strength of two different aluminum alloys AA5083-H111 and AA6351-T welded by using friction stir welding under varying process parameters with different tool pin profiles. The results showed that the joint fabricated by Straight Square at the tool rotational speed of 950 rpm yielded highest tensile strength of 273 MPa. The two process parameters affected the joint strength due to variations in material flow behavior, loss of cold work in the HAZ of AA5083 side, dissolution and over aging of precipitates of AA6351 side and formation of macroscopic defects in the weld zone.D. A. Dragatogiannis et al  did the work on 1 2 Department of Mechanical Engineering Ballari Institute of Technology & Management, Ballari, Karnataka, India Department of Mechanical Engineering Ballari Institute of Technology & Management, Ballari, Karnataka, India Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075 T651 And Aa 6061 T6 122 dissimilar friction stir welding between 5083 and 6082 Al alloys reinforced with TiC Nanoparticles. The optimum parameters selected are traverse speed of 60 to 85mm/min, rotational speed of 600 to 1180RPM and tool tilt angle 0°to 4°. The results shown that the hardness, elastic modulus, ultimate tensile strength, percentage of elongation, and yield values increase with the presence of TiC nanoparticles.D. M. Rodrigues et al  conducted the experiments on non-heat treatable AA 5083-H111 and heat treatable AA 6082-T6 aluminum alloys, which are widely used in welding fabrication. Welding is done under a large range of welding conditions with varying tool dimensions, rotation and traverse speeds, axial loads and tilt angles. Based on the various experiments, it is investigated that differences in friction stir weldability, weld defect and weld strength, is related to plastic behaviors of both base materials. Finally methodology for determining suitable friction stir welding parameters is proposed Hariharan et al  investigated the mechanical properties of Al 6061 & 7075 alloy using Computerized Numerical Control Machine by friction stir welding concept. The cylindrical & taper pin profile are selected and welding is carried out between 1600 to 1250 rpm at the rate of 120 mm/min with the tool tilt angle of 2°. High tensile strength of 485 MPa is produced at 1250 rpm,120mm/min and 2° tilt angle. The maximum hardness of 131 BHN is obtained at 1600 rpm. The taper tool at 1250 rpm has shown very fine grain structure 100µm due to the dynamic recrystallisation process. II. MATERIALS & METHODS A. Work Material Details– The two dissimilar aluminum alloys AA7075-T651 and AA6061-T6 are cut by milling machine of dimension 200x60x6.35mm. After the cutting the process work pieces are cleaned by acetone solution to remove the dust, dirt etc. The chemical composition of AA70705-T651is 0.05 %wt Si, 0.07 %wt Fe, 1.30 %wt Cu, 0.03%wt Mn, 2.69%wt Mg, 0.20%wt Cr, 0.01%wt Ni, 5.78%wt Zn, 0.06%wt Ti, 0.01%wt Pb, 0.01%wt Sn and balance aluminum. The mechanical properties of AA7075-T651 are 583.34 MPa ultimate tensile strength, 526.24 MPa Yield tensile strength, 11.26 total percentage elongation and 183.9 Vickers Hardness. Now the chemical composition of AA6061-T6 is 0.4 %wt Si, 0.7%wt Fe, 0.2%wt Cu, 0.15 %wt Mn, 1.20 %wt Mg, 0.35 %wt Cr, 0.15 %wt Ti, 0.25%wt Zn and balance aluminium. The mechanical properties of AA6061- T6 are 300 MPa ultimate tensile strength, 260 MPa yield strength, 19 percentage elongation and 110 Vickers Hardness. B. Tool Details – The joints of aluminum alloys are produced by five different tool profiles are used: threaded cylindrical (TC), triangular profile (TP), conical profile (CP), square profile (SP) and hexagonal profile (HP). High Carbon and high chromium steel is used as a tool material with shoulder diameter of 20 mm, tool pin diameter of 6.3 mm and pin length of 5.3mm. Tool material is an air hardened which has high wear and abrasion resistant properties. It is heat treatable and will offer hardness in the range 55-62 HRC, and is machinable in the annealed condition. Because of high chromium content it has mild corrosion resistance properties in the hardened condition. C. Selection of Process ParametersThe friction stir welding is carried out under three different process parameters, such as tool rotational speed of 750 RPM to 1250 RPM, welding speed of 90 mm/min to 110 mm/min and five different tool pin profiles as mentioned above. The photographic image of the welded specimens is shown in the Figure1. Figure 1. Welded Specimens II. RESULT AND DISCUSSION A. MacrostructureReferring to the figure 1, visual examination itself reveals that only two welds performed using square pin profile (Figure 1C) and hexagonal profile (Figure 1D) appears to be a good welded joint than any other pin profiles. Further it is observed that, during the welding process at 1000 rpm and 100 mm/min triangular profile tool has broken due to the lack of hardness, insufficient clamping force on the work piece, tool geometrical dimension and other parameters such as welding speed, tool rotation could be the possible reasons for the tool pin rupture. The five different types of tools used for friction stir welding and broken triangular profile is shown in Figure 2. The nugget zone and heat affected zone of welds produced from dissimilar aluminum alloys AA 7075 and A6061welded specimen are shown in Figure 3. The macro structure of the specimen 3 has no defect whereas the macro structure of specimen 4 has defect. The photographic images of the macrostructure of both the specimens are shown in Figure 4 Figure 2. Five different tool profiles Figure 3. Different zones of Welding Figure 4. Macrostructure of the Specimens 3 and 4 Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075 T651 And Aa 6061 T6 124 B. M icro structural StudiesMicro structural studies and tensile tests are envisaged for the two specimens (3 and 4) which appeared good quality welds through visual inspection as shown in Figure 5. Further specimen 3 is welded at 1250 rpm and 110 mm/min using square tool pin profile, whereas specimen 4 is welded at 1000 rpm and 100 mm/min using hexagonal tool pin profile. The interface zone between 7075 & 6061 shown for the specimen 3 in this, 7075 has undergone fragmentation and dynamic re-crystallization but 6061 has not changed its morphology. Similarly the interface zone between 7075 & 6061is shown for the specimen 4, in this, the 7075 undergone fragmentation and dynamic recrystallization, 6061 has not changed its morphology. By this it is understood no proper intermixing of alloys has taken place which will not give high joint strength. The photographic image of Microstructure of the specimens 3 and 4 are shown in Figure 6. Figure 5. Good Welds Figure 6. Microstructure of the Good quality welds C. Tensile StrengthThe ultimate tensile strength of the two specimens 3 and 4 are evaluated by preparing the tensile specimens as per ASTM E8M-04 standard. The prepared samples were tested on universal testing machine with a capacity of 50kN, make from Associate Scientific Engineering Works, New Delhi with gear rotation speed for gradual loading of 1.25, 1.5 and 2.5 mm/min. The prepared tensile specimen are shown in Figure 7. The specimen which is joined using hexagonal profile at 1000 rpm and 100 mm/min produced 35.46MPa and the specimen which is joined using square tool pin profile at 1250 rpm and 110 mm/min produced 125.41MPa. The stress-strain graphs of the specimen are shown in Figure 8. Figure 7. Tensile Specimens Figure 8. Stress – Strain Graph of Specimen 3 and 4 Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075 T651 And Aa 6061 T6 126 III.CONCLUSION The experimental investigation to find out the effect of tool pin profile on the on dissimilar friction stir welding on Aluminum alloys AA 7075 T651 and AA 6061 T6 which are used extensively in the aeronautical applications is successfully conducted using different process parameters like tool rotational speed, welding speed and tool pin profile. The following conclusions are drawn from the experimentation. a) The tool pin profile has greater impact on the tensile strength of the friction stir welded component. b) The good quality welds are possible with the application of sufficient clamping force on the work piece, proper design of tool geometrical dimensions with required tool hardness to avoid wreckage of tool, as in this case triangular tool profile has damaged. It is also seen that effect of tool pin profile augmented with tool rotational speed and welding speed on the tensile strength and micro structure of the material. c) The square tool pin profile and hexagonal tool pin profile at the tool rotation speed of 1250 rpm and the welding speed of 110 mm/min respectively produced good quality welds with tensile strength of 35kN and 125kN respectively in contrast to other tool pin profiles. d) The proper selection of tool pin profile, rotational speed, feed and other necessary parameters will give the better results. REFERENCES  Govind Reddy , Ch.Saketh , R. Padmanaban , V.Balusamy, Process Parameter Optimization for Friction Stir Welding of dissimilar Aluminum Alloys, International Journal of Engineering Research & Technology (IJERT), Vol. 2 Issue 10, October – 2013.  M. Koilraj , V. Sundareswaran , S. Vijayan , S.R. Koteswara Rao, Friction stir welding of dissimilar aluminum alloys AA2219 to AA5083 – Optimization of process parameters using Taguchi technique, Materials and Design 42 (2012) 1–7.  D. M. Rodrigues, C. Leitão, R. Louro, H. Gouveia & A. Loureiro, High speed friction stir welding of aluminium alloys, Science and Technology of Welding and Joining,15:8, 676-681.  D. A. Dragatogiannis, E. P. Koumoulos, I. A. Kartsonakis, D. I. Pantelis, P. N. Karakizis & C. A. Charitidis, Dissimilar Friction Stir Welding Between 5083 and 6082 Al Alloys Reinforced With TiC Nanoparticles, Materials and Manufacturing Processes, 31:16, 2101-2114.  R. Palanivel , P. Koshy Mathews , N. Murugan , I. Dinaharan, Effect of tool rotational speed and pin profile on microstructureand tensile strength of dissimilar friction stir welded AA5083-H111 and AA6351-T6 aluminum alloys, Materials and Design 40 (2012) 7–16.  R. Hariharan and R.J. Golden Renjith Nimal, Friction Stir Welding Oof Dissimilar Aluminium Alloys (6061&7075) By Using Computerized Numerical Control Machine, Middle-East Journal of Scientific Research 20 (5): 601-605, 2014.  Ranjith. R, Senthil Kumar. B, “Joining of dissimilar aluminium alloys AA2014 T651 and AA6063 T651 by friction stir welding process”, WSEAS Transactions On Applied And Theoretical Mechanics, E-ISSN: 2224-3429, Volume 9, 2014.  N. Shanmuga Sundaram , N. Murugan, “Tensile behavior of dissimilar friction stir welded joints of aluminium alloys”, Materials and Design 31 (2010) 4184–4193.  P. Cavaliere, R. Nobile, F.W. Panella, A. Squillace, “Mechanical and microstructural behaviour of 2024–7075 aluminium alloy sheets joined by friction stir welding”, International Journal of Machine Tools & Manufacture 46 (2006) 588–594.  N. T. Kumbhar and K. Bhanumurthy, “Friction StirWelding of Al 5052 with Al 6061 Alloys”, Journal of Metallurgy, Hindawi Publishing Corporation.