A Study of the Optimization and Characterization of Friction Stir Welded AA5083 and AA6082

Mullaiarasu R.1 , Thilagham K. T.2, Noorullah D.3 1PG Scholar, Department of Metallurgical Engineering, Government College of Engineering, Salem, Tamilnadu, India. 2Assistant Professor, Department of Metallurgical Engineering, Government College of Engineering, Salem, Tamilnadu, India 3Head of the Department, Department of Metallurgical Engineering, Government College of Engineering, Salem, Tamilnadu, India


Introduction
Friction stir welding has seen significant advancements and improvements in light weight construction. Because the temperature involved in this method is significantly lower than the melting point of the base material, it is commonly used for welding of similar and dissimilar materials, whether secondary phases occur or not (Mori and Abe Ahn et al.). The heat produced by stirring the nonconsumable rotating tool used for metal bonding. It can be used to join aluminium, copper, magnesium, lead, and steel plates. The process is environmentally friendly because no protective gases are used in the process. Fathi, Jalal, et al (Fathi). observed that tool tilt angle has an effect on all three responses, positively influencing tensile strength, yield strength, and percentage elongation. Tensile strength of 210 MPa, yield strength of 203 MPa, and percent elongation of 12 were recorded using a tool with a shoulder diameter of 18mm, a 0mm offset, and a 1 • tilt angle (Kumar, M, and Ramana Gao Chen). Hassan, Malik, et al. (Hassan) investigated the effect of tool tilt angle on the mechanical properties of dissimilar aluminum and copper alloys at 0, 1, 2, 3, and 4 0 tilt angles. The results showed that defect-free joints were produced with a high joint strength of 117 MPa and hardness of 181VHN at the nugget area at a tool tilt angle of 4 degrees. Ahn, J., et al. (Ahn) successfully welded 6.45 mm thick 5086H32 aluminum alloys using TIG, MIG, and FSW processes, and the results showed that FSW joints had better tensile properties than fusion welded joints. Hasan, Mohammed M., et al. (Hasan) investigated the tensile strength of the dissimilar joint (AA2014 & AA6082) and con-cluded that low rotational speed, lower travel speed, and lower tilt angle give more tensile strength. The ideal variables were 600rpm rotational speed, 60mm/min welding speed, and a 1 • tilt angle. The optimum parameters where high impact value on characterization results were obtained (Kumar, M, et al. Mugada, Adepu, et al.).
Dinesh et al. investigated the greater tensile strength of (AA7075&AA6082) of 217 MPa and reported that medium rotational speed, lower welding speed, and tilt angle were all important factors (Thilagham, Muthukumaran, et al.). It increases the tensile strength of the upper and lower values. The ideal settings are 900 rpm rotational speed, 90 mm/min welding speed, and a tilt angle of 2 0 . From the aforementioned literature review, it is obvious that the FSW method may be applied to different alloys, and that investigations on dissimilar FSW of AA5083 and AA6082 may be carried out using a constant process parameter (Chander Grover and Singh Sharma).
Previously Khorramian, Koosha, (Khorramian and Sadeghian), investigated fusion welding of AA5083, whereas Mahendrakumar Madhavan. (Selvaraj and Madhavan) and Saravanakumar, R, et al (Saravanakumar et al.), were investigated FSW optimization and defect minimization on this 5083-H321 armor grade alloy. Similarly, the optimization and investigation of process parameters for defect-free with better mechanical and metallurgical qualities joint is investigated here. The impact of process parameters on the mechanical properties of dissimilar FSW welds of AA5083&AA6082, which are often used in shipbuilding, was investigated in this study.

Materials and Methods
Dissimilar aluminium alloy plates (AA6082 & AA5083) are made to the specified dimensions (100X50X6 mm 3 ). The Chemical composition and mechanical properties of AA5083 and AA6082 in are listed in Tables 1. and Table 2. Proper tool material selection is necessary for a high-quality weld. As illustrated in Figure 1, Tool Design and Dissimilar samples of high-speed steel with a cylindrical pin profile tool was employed in this study. Following the completion of the welding using the FSW-3T-Hydralic milling machine, the samples were prepared for tensile testing using EDM wire cut in con-formity with applicable standard. The Tensile Failure AA6082/AA5083 samples are shown in Figure  2.
The studies are then carried out to determine the optimal working level of Process Parameters in Table 3. shows the values that were observed in experiments. To improve mechanical properties, the AA6082 is on the advancing side and the AA5083 is on the retreating side. Table 4. shows the Design of experiment for Taguchi L9 orthogonal array for welding AA6082 and 5083.
The tensile testing on the UTM machine was then characterized according to the ASTM E8/E8M-09 standard. The samples were also etched for 15 seconds with Keller's reagent (190ml water, 5ml HNO3, 3ml HCL, and 2ml HF) to examine the microstructure and microhardness of the welds in different zones.

Ultimate Tensile Strength
The Tensile test result of AA6082/AA5083 Friction Stir Welded Samples is shown in Table 5. The Tensile Failure of AA6082/AA5083 samples is shown in Figure 2. Rotational speed 1200rpm, travel speed 120mm/min; tilt angle (1 • ) yielded a maximum tensile value of 207.49 MPa. Tensile failure was seen in the joints on AA6082 of the weld, and HAZ due to excessive heat liberation on the advancing side. The tensile failure of the tool tilt 0 • AA6082/AA5083 welds is on the AA5083 of the weld, due to tunnel faults on the retreating side of AA5083.

Taguchi Analysis
The Taguchi L9 orthogonal technique was used to improve the parameter for friction stir welds AA6082/AA5083. The optimized parameter and plot graph on mean and SN/ratio are presented below. The tensile strength response of AA6082/AA5083 is shown in Table 6. and the Main effects plot for SN Ratios and Means are shown in Figure 3. The response table for signal to noise ratios for larger is better demonstrates that tilt angle has the greatest influence on tensile strength, followed by rotational speed, and then travel speed. The findings revealed revealed that rotating speed of 1200 rpm,    Figures 4 [a,b]. The response table for signal to noise ratios for greater is better clearly illustrates that tilt angle has the greatest influence on yield strength, followed by rotational speed, and then travel speed. The Figure depicts that higher yield strength was found on rotational speed 900 rpm, travel speed 60 mm/min, and tilt angle 1 • .  The % elongation response of AA6082/AA5083 for SN ratio and Mean is shown in Table 10 & 11, and the main effects of the percent elongation response of AA6082/AA5083 for SN ratio and Mean are shown in Figures 5 [a, b]. The response table for  signal to noise ratios for greater is better clearly illustrates that travel speed has the greatest influence on percent elongation, followed by tilt angle, and then rotational speed. The graph demonstrates that higher elongation was found on rotational speed 600 rpm, travel speed 90 mm/min, and tilt angle 1 • .

Discussion
With the aid of software Minitab21, the optimum parameters of AA6082/AA5083 friction stir welds SNL -"Larger is better" case is determined using S N = 10 xlog(Σ ( 1 Y 2 )/n ) (i) Where, Y is the experiment at the test and n is the total number of trials in the test. Finally, Table  13 is showing the Optimum Parameter values for the AA6082/AA5083 weld in terms of Maximum Tensile Strength, Maximum Yield Strength and Maximum Elongation.  Figure 6a.
On AA6082BM, the microstructures reveal α-solid solution of aluminum-magnesium-silicon with its intermetallic, whereas on non-heat treatable AA5083BM, the microstructures indicate α-solid solution of aluminum-magnesium solid solution with its intermetallics. The AA6082HAZ and AA5083HAZ represent coarse grains, whereas the weld zone represents refined and recrystallized grains.

Macro Examination
The Macrostructure of FSW samples i.e., AA6082/5083 welds is shown in Figure 7. The macrostructure of several zones such as base metal, HAZ, TMAZ, and Stir zone was demonstrated. On the advancing side, the weld nugget has a basin shape, whereas on the retreating side, it has a flash projection. Table 13. shows the Hardness Profile of FSW AA6082&AA5083 and Figure 8. Shows Hardness survey of samples AA6082&AA5083 measured for several weld specimens in various zones. The high microhardness of 90.5 HV attained in the different AA6082 and AA5083, which have a rotational speed of 1200rpm, a travel speed of 120 mm/min, and a tilt angle of 1 • , respectively. While the tilt angles were 1 0 and 2 0 , the hardness values in AA6082HAZ decreased, and tensile failures were observed. Moreira et al., reported with the lower hardness in AA6082HAZ in AA6061/AA6082 weld. Similarly, there was a drop in harness when tilt angles were 0 0 at the AA5083WN weld zone were seen. tilt angle is perpendicular to the workpiece surface, and extremely plastic embedding occurs as a result of material ejection as slip in the weld entry zone, leaving a tunnel defect in the area of material loss.

Conclusion
The friction stirs welding of dissimilar AA6082-T6 and AA5083 H-111 was successfully completed under the impact of welding conditions, and the following interferences were drawn. Dissimilar aluminium alloys AA6082 (advancing side) and AA5083 (retreating side) have been welded using friction stir welding. At a tool rotational speed of 1200 rpm, a travel speed of 120 mm/min, and a tilt angle of 1 • , the highest tensile strength of 207.49 MPa was achieved. At a tool rotational speed of 1200rpm, a travel speed of 90mm/min, and a tilt angle of 0 • , the lowest tensile strength of 113.5 MPa was observed. At dissimilar welds, the tensile strength was found to be 150.71 MPa (Advancing side AA5083 & Retreating side AA6082). The higher tensile strength was 207.70 MPa on a similar weld of (AA6082& AA6082). On the advancing and retreating sides of the base metal areas, the microstructure exhibits -solid solutions of AA6082 and AA5083 along with their intermetallic. The microhardness of the weld zone in a dissimilar joint with weld parameters of rotational speed 1200 rpm, travel speed 120 mm/min, and tilt angle 1 • is 90.5 HV, which is greater than either AA6082BM or AA5083BM. When welding settings of tilt angle 0 • was applied, tunnel defects and tunnel voids appeared on the retreating side of the AA5083 weld.
5. Future Work SEM analysis, XRD and Corrosion studies in immersion testing of electrochemical corrosion for dissimilar joints are planned to conduct in future.

Data Availability Statement
All data that support the findings of this study are included within the article (and any supplementary files) ORCID iDs Mullaiarasu R. https://orcid.org/0000-0001-7768-0057