MICROSTRUCTURE TESTING STIR WELDING T-JOINTS OF AL ALLOY

Transcription

1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 5, May 017, pp , Article ID: IJMET_08_05_035 Available online at aeme.com/ijmet/issues.asp?jtype=ijmet&vtyp pe=8&itype=5 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed HARDNESS AND MICROSTRUCTURE TESTING OF FRICTION STIR WELDING T-JOINTS OF AL ALLOY Gyan setu Assistant Professor, Department of Mechanical Engineering, K L University, Vaddeswaram, Andhra Pradesh, India. B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, B.Satya Akhil U.G Student, Department of Mechanical Engineering, K L University, Vaddeswaram, Andhra Pradesh, India. ABSTRACT Friction Stir Welding is a solid state welding process which uses a special tool to generate heat unlike other conventional processes. It is a green welding process as it doesn t produce fumes and harmful gasses during machining. It is vastly used in industries like aerospace and automobile for sound weld. Welding is produced by impugning the rotating tool axially into the surface of joints. Tool rotational speed, welding speed, axial force and number of passes are some process parameters for sound welds. In this paper friction stir welding of Al alloy by T- joint is performed. Tool rotational speed and number of passes is the processs parameter for experimentation. Hardnesss and microstructure test is done for nugget zone by brinell hardness and optical microscope. Keywords: Friction stirs welding, T joint, Tool rotational speed, Number of passes Cite this Article: Gyan setu, B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, and B.Satya Akhil Hardness and Microstructure Testing of Friction Stir Welding T- Joints of AL Alloy. International Journal of Mechanical Engineering and Technology, 8(5), 017, pp IType=5 INTRODUCTION Friction stir welding (FSW) is a solid-state welding process where the specially designed nonrotating tool axially consumable tool is used for welding. The basic principle is to plunge the into the surface of joint which consists of tool shoulder and probes. Tool shoulder creates friction between tool and surface whereas probe is used to penetrate into the surface. The schematic diagram of FSW process is shown in Figure 1. T L Teng et al. mentioned that T welded joint is a kind of fillet joint where it is used in various support frames, pressure vessels and bridge structures. The conventional welding editor@iaeme.com

2 Hardness and Microstructure Testing of Friction Stir Welding T-Joints of AL Alloy process causes residual stresses in the material which have low mass to volume ratios, to overcome these defects friction stir welding is considered as the best alternative(1). According to G. Buffa et al. and Franti et.al FSW of an Aluminium T-joint can be described in three stages where the first stage is of filling the joint fillets which deforms the material plastically requires a larger tool shoulder(). The next stage is the material flow that must be in the axial direction and it plays an important role in the bonding between the skin and the stringer where the geometry of the pin and the angle of tilt play a crucial role. The last step is to provide optimum tool parameters for sound welds in this step. Esther T. Akinlabi et al. analysed that the axial force influences the ultimate tensile strengths of welds (7). L V Kamble et al. concluded that the square tool pin provides a sound weld compared to other profiles (6). A.C.F Silva et.al derived by ANOVA techniques that the strength of the joint is influenced by the tool rotational speed (11). R Rai et al concluded that for Al alloys gives best result with HSS steel for the tool(5). D Venkateswarlu et al. analysed the various pin profiles and concluded that taper tool profile is the best to produce joints for flat plates (10). Zang et al said about the tool dimensions based on the material thickness (8). N Rajamanickam and V Baluswamy considered the tool rotational speed (TRS), welding speed (WS) and axial force (AF) as the process parameters which decides the quality of welds(3). T Deb Roy et al also considered the axial force and tool rotational speed as the process parameter. The other process parameter which needs to be considered is the number of passes which is not considered till this instinct (4). In this paper number of passes along with the tool rotational speed is considered as the process parameters and hardness profiles along with the microstructure of the nugget zone is observed. Figure 1 Schematic diagram of friction stir welding. EXPERIMENTAL PROCEDURE Friction stir welding (FSW) experiment of T-Joint is carried out on eight AA64430 plates. The hardness and the ultimate tensile strength of the material are 77.5 BHN and 77.5 MPa respectively. AA64430 sheets of thickness 5mm cut into blanks of dimensions 100x50x5 mm for skin and 50x50x5 mm for stringer. The chemical composition of the material is obtained from optical emission spectrometer and the details are given in the Table editor@iaeme.com

3 Gyan setu, B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, and B..Satya Akhil Table 1 Chemical composition of AA Grade Mg AA Si Fe Mn Zn Ti Cr Al Rem The T-Lap joints performed on vertical milling machine by varying the rpm and the no passes i.e. one and two pass. A special fixture was designed for holding the skin and stringer shown in the Figure-. Figure Fixture for holding the skin and stringer. The tool is modelled as per the dimension given by Zhang et al. in solid works version Shoulder diameter (D) =. * work piece thickness (t) And probe diameter (d) = 0.8 * sample thickness (t) +. Figure 3 Figure 4 Figure 3. Tool along with dimensions Figure 4. Tool modeled in solid works The schematic diagram of tool is shown in Figure-3 and 4. Tool is made of HSS steel and manufactured in two stages where the first top shoulder is made with a thickness of 0mm editor@iaeme.com

4 Hardness and Microstructure Testing of Friction Stir Welding T-Joints of AL Alloy and the pin is made with a tapered surface of diameter 5mm at the shoulder end and 3mm at open end. The length of the pin is 8mm for the complete penetration of tool into the skin and the joining edge of the stringer. The composition of the HSS is mentioned in the following Table-. Table Chemical composition of High Speed Steel HSS. Grade T Cr V C Fe HSS Rest The traversed speed is kept constant as 0mm/min and the rotational speed varies as 710rpm, 900rpm, 110rpm and 1400rpm. T lab joint weld is in single sided by varying the number of passes as one and two pass for a particular speed. The welding parameters are given in the Table 3 by naming A, B, C & D for 710, 900, 110 and 1400rpm respectively. DESIGNATI ON FOR JOINT Table 3 Process parameters. TOOL ROTATION AL SPEED (RPM) WELD SPEED (mm/min) NO. OF PASS ES A A B B C C D D To observe the changes in the microstructure by due to one and two pass in the nugget zone the microstructure images are taken under the optical microscope and the hardness values are performed on the Brinell s hardness testing machine. RESULTS AND DISCUSSIONS HARDNESS Figure 5 and 6 shows the hardness behaviour for different transverse rotational speed (TRS) due to one and two pass at the skin side of the joint. These hardness profiles are taken in the nugget zone. The material in the nugget zone undergoes typical plastic deformations and which would in turn causes dynamic recrystallization Hardness measurements are taken using Brinell s hardness at the nugget zone by applying a load of 50kg. There is no significant change in the hardness values for the joints of one and of two pass observed. But it is worthy pointing out that hardness number decreases with the increase in the TRS for one pass and there is fluctuation in the values of hardness for two pass. There is a decrease in the hardness values compared with the base material. Figure 7 shows the hardness behaviour of the material with respect to the number of passes and it can be observed there is no huge deviation of hardness values for one pass and two pass. So it can be concluded that number of pass is not an important parameter to consider. The hardness values for each indentation and for each RPM are shown in the Table editor@iaeme.com

5 Gyan setu, B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, and B.Satya Akhil Figure 5 Hardness vs. TRS for one pass. Figure 6 Hardness vs. TRS for two pass. Figure 7 Hardness vs. number of passes at 710 rpm editor@iaeme.com

6 Hardness and Microstructure Testing of Friction Stir Welding T-Joints of AL Alloy Figure 8 Hardness vs. number of passes at 900 rpm Figure 9 Hardness vs. number of passes at 110 rpm Figure 10 Hardness vs. number of passes at 1400 rpm editor@iaeme.com

7 Gyan setu, B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, and B..Satya Akhil MICRO STRUCTURE Table 4 Hardness number for tool rotation speed and number of passes Tool rotation speed The microstructure analysis is done using optical microscope of magnification 10µm. Analysis is done at the nugget zone using ASTME11 Standard. It is observed that the grain size is increased with increase total rotation speed. The grain size is being showed in the Table-5 w.r.t TRS and no of passes. the micro structural images are taken for TRS of 710 and 1400 rpm. The obtained images are shown in the Figure Equiv.-axed grains are obtained at the nugget zone which indicates the recrystallization of grains. It occurs because of sufficient heat input to form homogeneous grains It can be observed that there is no change in the grain size of the samples for one pass and two pass. This shows that change in the number of passes has no effect on the microstructure. During the analysis, no defects were found in the nugget zone. It can be seen that the grain size is being increased with increase in the RPM from 710 to The graphs are plotted based of the grain structure and the tool rotational speed as shown Figure Table 5 Grain size w.r.t TRS and number of passes. Tool rotational speed (RPM) No of pass No of passes Hardness Number (BHN) Grain size(mm) Figure 111 Micro structural image of 710 rpm in one pass editor@iaeme.com

8 Hardness and Microstructure Testing of Friction Stir Welding T-Joints of AL Alloy Figure 1 Micro structural image of 710 rpm and two pass Figure 15 Variation in grain size at 710 rpm TRS for one and two pass. Figure 13 Micro structural image of 1400 rpm in one pass editor@iaeme.com

9 Gyan setu, B.Sai Sandeep, A.Praveen Kumar, B.V. Akshay Kumar, and B..Satya Akhil Figure 14. Micro structural image of 1400 rpm and two passs. CONCLUSION Figure 16 Variation in grain size at 1400 rpm TRS for one and two pass. By varying the no of passes there is no much change in the hardness values is observed and the grain size also remained the same 1. The hardness values are decreased with an increase in rpm. The hardness values did not vary by an extent by varying no of passes 3. It can be observed that the hardness number decreased with increase in the rpm for one pass but for two passes there is a fluctuation in the hardness values 4. The grains obtained are fine due to the proper optimized parameters. 5. There is no change in the size of the grains for one pass and two pass 34 editor@iaeme.com

10 Hardness and Microstructure Testing of Friction Stir Welding T-Joints of AL Alloy REFERENCES [1] T.L. Teng, C.P. Fung, P.H. Chang, W.C. Yang, Int. J. Press. Vessels Pip. 78 (001), [] L. Fratini, G. Buffa, L. Filice, F. Gagliardi, P I Mech. Eng. B: J. Eng. 0 (006) [3] N Rajamanickam & V.Balusamy effect of process parameters and mechanical properties of friction stir welds using design of experiments. Indian journal of engineering & material scinces vol.15,august 008,pp [4] T. DebRoy and H. K. D. H. Bhadeshia Friction stir welding of dissimilar alloys a Perspective Science and Technology of Welding and Joining 010 VOL 15 NO 4. [5] R. Rai, A. De, H. K. D. H. Bhadeshia and T. DebRoy Review: friction stir welding tools Science and Technology of Welding and Joining 011 VOL 16 NO 4. [6] L.V. Kamble, S.N. Soman, P.K. Brahmankar Effect of Tool Design and Process Variables on Mechanical Properties and Microstructure of AA6101-T6 Alloy Welded by Friction Stir Welding SR Journal of Mechanical and Civil Engineering (IOSR-JMCE) 01 PP : [7] Esther T. Akinlabi and Stephen A. Akinlabi Friction Stir Welding of Dissimilar Materials. [8] Statistical Analysis of the Weld Data International multiconference of engineers and computer scientists 01 vol II. [9] Y. N. Zhang, X. Cao*, S. Larose and P. Wanjara Review of tools for friction stir welding and Processing Canadian Metallurgical Quarterly 01 VOL 51 NO 3. [10] Lei Cui, Xinqi Yang, Guang Zhou, Xiaodong Xu, Zhikang Shen Characteristics of defects and tensile behaviors on friction stir welded AA6061-T4 T-joints Materials Science and Engineering A 543 (01) [11] D. VENKATESWARLU, N. R. MANDAL, M. M. MAHAPATRA, and S. P. HARSH Tool Design Effects for FSW of AA7039 WELDING JOURNAL pp [1] N Ravinder Reddy and G Mohan Reddy, Friction Stir Welding of Aluminium Alloys - A Review, International Journal of Mechanical Engineering and Technology, 7(), 016, pp [13] Somashekara Koushik Ayalasomayajula, Examining The Mechanical Properties of Annealed and Not Annealed Multilayer Film (Polyethylene/ Polyethylene Terephthalate/ Polyethylene) by Dynamic Mechanical Analysis (DMA), International Journal of Mechanical Engineering and Technology, 6(10), 015, pp [14] Cherian Paul, Parvathy Venugopal, Modelling of Interfacial Heat Transfer Coefficient and Experimental Verification for Gravity Die Casting of Aluminium Alloys., International Journal of Mechanical Engineering and Technology, 7(), 016, pp [15] Ana C.F. Silva Daniel F.O. Braga M.A.V. de Figueiredo, P.M.G.P. Moreira Friction stir welded T-joints optimization Materials and Design 55 (014) editor@iaeme.com