Optimization of Process Parameters in Under Water Friction Stir Welded AA2014 and AA6082 joints.

This work focuses on optimizing process parameters in underwater friction stir welding to study their impact on the mechanical characteristics of aluminum 2014 T6 and 6082 T6 joints. The aluminum plates are precisely machined to provide the necessary polish for the underwater friction stir welding process (UFSW). Experiments are designed using Taguchi L-9 orthogonal array, considering three process parameters: speed, transverse speed, and tool angles at three levels each. The aluminum plates of series 2014-T6 and 6082-T6 are securely installed in the machine. The plates will be welded using the UFSW process using a taper pin tool. The welded plates are next subjected to tests to assess their mechanical qualities. Tests for tensile strength, hardness, and impact strength are conducted on the welded area of the plate to determine its mechanical qualities. An ANOVA was conducted to determine the significant influence of each variable. The optimal values achieved are Tensile Strength of 185.592 N/mm2, Hardness of 75.1 (BHN), and Impact Strength of 21.236 Joules at a speed of 1120 rpm, transverse speed of 80 mm/min, and tilt angle of 2 degrees.


Introduction
Friction Stir Welding (FSW) is a process or method which is used to join two different materials by plasticization the welded zone of solid bodies to be connected and by its solidification after cooling.This process is increasingly use in world widely in ship building industries, Rail industries, Electronics and Electrical appliances, etc. Underwater Friction Stir Welding has a rotating and a penetrating tool which penetrates the place where it melts and mixes the semi molten metal with friction heat, in the place of welded place an onion ring structure is formed.Then the welded plates are exposed to mechanical tastings like Tensile, Hardness and Impact test, and the results are recorded which will be practical side of experiment.
FSW aims to examine and summarize several elements of UFSW.Emphasis is placed on fundamental concepts such as material flow, temperature production, process parameters, microstructure, and mechanical qualities.[1][2][3].The rotating welding device is slowly inserted into the workpiece until the shoulder of the welding tool makes firm contact with the top surface of the material.[4].Underwater friction stir welding is a preferred method to address the challenges posed by low heat input and short dwell time in processing dissimilar joints of AA6082/AA8011.The pin profile has a significant impact on the microstructure and mechanical properties of the welded joint.Hard and brittle IOP Publishing doi:10.1088/1742-6596/2765/1/012025 2 precipitates occur at the weld bead due to the difference in peak temperature of UFSW compared to air friction stir welding (AFSW), making it more problematic.[5][6].A curved interface forms due to increased materials mixing at the advancing side, resulting in a linear hardness gradient across the dissimilar weldment.The computational time for the firefly optimization-based texture in the heat affected zone was found to be nearly equivalent to that of the base material and simple shear [7].The mechanical properties of the aluminum alloy 6082-T6 joint are influenced by the process parameters of underwater friction stir welding.Various evolutionary optimization approaches are used to describe this process [8].Electron backscatter diffraction technique was utilized to analyze microstructural changes and texture evolution in different 7003/6060 aluminum alloys during underwater friction stir welding [9] Microstructural analysis showed that most fractures are located in the thermomechanically damaged zone [10].An experimental study examined the ultimate tensile strength (UTS) of weld joints created by Friction Stir Welding (FSW) and Ultrasonic Welding with Friction Stir Welding (UWFSW) utilizing a newly developed fixture to tackle post-process problems [11].Examining the weldability of aluminum and silicon carbide metal matrix composite components containing 10% silicon carbide by utilizing a TiAlN coated tool in the friction stir welding process.A CNC milling machine is used for Friction Stir Welding (FSW).Aluminum plates from series 6061 and 7075 are firmly fastened to the machine [12][13].The study examines the recrystallization mechanism, grain boundary characteristics, phase transformation, texture evolution, characteristic microstructures, and their effects on the hardness, tensile strength, fatigue properties, and superplastic behavior of aluminum alloys processed using friction stir welding/friction stir processing [14].An underwater friction stir welding technique is used on aluminum alloy 6082-T6 to develop a mathematical model for optimizing process parameters and obtaining the highest tensile strength [15].Optimizing friction stir welding (FSW) parameters to achieve both high tensile strength and impact toughness using Taguchi-based Greyish Relational Analysis (GRA) and Artificial Neural Network (ANN) [16][17][18].An investigation is conducted on how input operating process factors, such as tool rotating speed (TRS), feed rate, and pitch values, affect output response parameters like ultimate tensile strength (UTS) and hardness of welded connections.[19,20] Regression models in mathematics were employed to predict the ultimate tensile strength and tensile elongation of custom welded joints [20][21].Friction stir welded dissimilar alloys may be shaped by modifying three crucial process parameters: tool rotating speed, weld speed, and tool tilt angle.Various combinations of sheets were used for experimental and finite element modelling testing to assess the maximum dome height [22][23][24].

2.Experimentation
Friction stir welding (FSW) of aluminum alloy was performed using a modified milling machine.The gadget would have operated at an optimal speed of 1800 revolutions per minute with a power output of 5.5 kilowatts per revolution.The materials used for this project are Al 6082 T6 alloy and Al 2014 T6 rolled plates with specified compositions as shown in the table.The counter plates have been ground at the optimal location with welding completed prior to further processing.Work out parts has been ready with respective duration, thickness, width.The metal plates are securely installed into the apparatus shown in Figure 1.A hardened High-Speed Steel (HSS) tool was used to machine a shoulder with a diameter of 16mm, a pin with a taper diameter of 6mm, and a length of 2mm.This device is equipped in the equipment holder as well as career portion is rigidly clamped to printer kitchen table making use of fixtures.The water is flow through the welded surface the heat transfer through it.It is act as a coolant for under water friction stir welding.

Selection of materials
Aluminium alloy 6082 is a moderately robust alloy with excellent resistance to oxidation.It has the highest strength among the 6000 series alloys.Alloy 6082 is acknowledged as a structural alloy.
Aluminum alloy 6082 has good machinability and forms tight coils of metal chips when chip breakers are used in the T651 and T6 temper conditions.aluminum 2014 may be tempered during machining and is likely one of the strongest lightweight aluminum alloys, boasting high hardness.The chemical composition of aluminum alloys is displayed in Table 1.It is the second most recognized lightweight aluminum alloy in the 2000 series.

Selection of Machining Paramteres
The procedure parameters are chosen based on the literature review.The input variable is "selected Speed" in revolutions per minute (rpm).Transverse Speed (TS) in mm/min, Tool angle in degrees Various levels of each process parameter is mentioned.Welded area undergoes mechanical property testing.Tensile strength, hardness, and impact strength Table 2 displays the UFSW parameters utilized in the experiment.The process parameter experimental design is conducted using MINITAB software.The Taguchi approach involves designing trials using an L-9 orthogonal array.. Friction Stir Welding is solid state welding process where friction acts to weld, in this aluminium 2014 T6 and aluminium 6082 T6 is taken because aluminium is the one of the lightest materials in present living world.Figure 1.Tested specimens and Underwater FSW First the plates are welded by process called FSW and they cut in ASTM standards and sent to mechanical tests like Tensile, Hardness and Impact.The underwater friction stir welding machine and welded joint After the mechanical testing is performed the outcome of those are saved and values are noted.Then particle and predicted values are compared, for predicted values we are using L9 orthogonal array where there should be 9 specimens for each testing.We use a software called MINITAB where TAGUCHI and ANOVA module is used and made some numerical calculations are performed.Hence showing that practice and predicted are approx.same

3.Mechanical Properties Evaluation
The mechanical properties are evaluated on FSW welded joints.The performed tests are Hardness test, Tensile test, and Impact test.

Hardness Test
This basic sequence of examination pressure program proved to become a significant advance within the realm of hardness tests.The user was enabled by it to do a precise hardness test on an assortment of sized areas inside only several seconds.The analysis of Hardness with help of Main effects plot from increase of speed, transverse speed and tool angle the hardness increase up to 900rpm,60 mm/min and 2 0 later decreases as shown in Figure 2 Table 3 From Table3.we can acknowledge that percentage of contribution by the three parameters like speed in rpm is 74.23%, transverse speed is 10.18%, angle in degree is 11.36% and we can calculate percentage of error recorded.
By observing the graph of SN ratio and mean of mean value graph in Figure3.wechoose optimum values at larger point in hardness test we consider larger value is better, so we have tool speed in rpm at 1120, transverse speed of feed at 80 mm/min and tool angle is at 2º Figure 3. SN ratio plot for hardness

3.2Tensile Test
A tensile check, likewise, recognized like a stress check, is among the majority of essential as well as typical kinds of physical tests.A tensile check is applicable tensile (pulling) pressure to a substance and measures the specimen 's reaction on the anxiety.The analysis of Tensile strength with help of Main effects plot from increases of speed and transverse speed the tensile strength increases and increase of tool angle the tensile strength is increase up to angle of 2 0 later decreases as shown in Figure 4.  4. We can acknowledge that percentage of contribution by the three parameters like tool speed in rpm is 39.27%, transverse speed of feed is 29.22%, angle in degree is 30.02% and we can calculate percentage of error recorded.By observing the SN ratio and mean of mean value graph in Figure 5. we choose optimum values at larger point as in tensile test we consider larger value is better, so we have tool speed in rpm at 1120, transverse speed at 80 mm/min and tool angle is at 2º

3.3Impact Test
A greater strength material is going to absorb a lot more power upon influence.The analysis of impact strength with help of Main effects plot from increase of speed the impact strength is linear up to 900rpm later decreases, the increase of transverse speed the impact strength increases up to 60 mm/min later decreases and increase of tool angle the impact strength is increase up to 20 later decreases as shown in Figure 6.From this Table 5 we can acknowledge that percentage of contribution by the three parameters like speed in rpm is 59.83%, transverse speed is 18.70%, angle in degree is 14.17% and we can calculate percentage of error recorded.
By observing the graph of SN ratio and mean of mean value graph in Figure 7 we choose optimum values at smaller point in impact test we consider smaller value is better, so we have tool speed in rpm at 1120, transverse speed of feed at 80mm/min and tool angle is at 2º Figure 7. S/N ratio plot for impact strength

Validation
To validate the experiment, we need to compare the practical values and predicted optimum values from which we can justify optimum parameters of friction stir welding of aluminum 2014 T6 and aluminum 6082 T6 are Table 6.By the observation from the above tables of practical and theoretical Validation studies are required since the optimal circumstances for different responses are found to be beyond the scope of the L-9 orthogonal array.The validation run is conducted under the ideal circumstances specified in Table 6.To compare with the projected optimal response levels.The optimal anticipated values for hardness, ultimate tensile strength (UTS), and impact determined from regression analysis for experimental data are derived from equations 1-3.The average discrepancy between the projected and experimental results is 10.42%, indicating that the accuracy of the development models is 89.57%.We tabulate the predicted optimum values corresponding to practical optimum value for mechanical testing according to their parameters.From these the optimized best parameter value for welding of aluminum plates is at speed of tool in rpm 1120, transverse speed of feed 80mm/sec and angle in degree 2º.At which predicted values and practical optimum values are relevant equal, so I conclude these parameters of tensile, hardness and impact test are optimal values for underwater friction stir welding.

4.Conclusions
The experiment was conducted to establish the optimal conditions for underwater friction stir welding.The methodology presented in the thesis can be implemented in manufacturing units or production lines to determine the most effective values of welding parameters (speed, transverse speed, tool angle) in order to enhance weld strength, improve surface quality of the welded area, ensure weld quality, and prevent potential deterioration of weld mechanical properties.
1. Optimum solutions for tool speed in rpm and transverse speed of feed are obtained by Taguchi method.And it is shown that the angle of tool should not be higher than 2º. 2. It is shown that with the increasing of tool speed and temperature in welding zone, the weld becomes stronger (for the case of joining aluminum 2014 T6 with aluminum 6082 T6).
3. It can be concluded that optimal welding parameters predicted by ANOVA (speed in rpm, transverse speed, tool angle) and practical values of welding parameters from experiments are approximately the same.Realization of these optimal parameters will make it possible to receive the best welding surface and increased strength characteristics.4. Optimal welding parameters are determined with the Taguchi method.These optimal parameters are as follows: speed of tool is 1120 rpm; transverse speed of feed is 80mm/sec and angle of tool is 2º (for the case of Underwater friction stir welding of details from aluminum 2014 T6and aluminum 6082 T6).

Figure 2 .
Main effects plot for Hardness

6 Figure 4 .
Figure 4. Tested specimens and Main effects plot for tensile

7 Figure 5 .
Figure 5. S/N ratio plot for tensile strength

Figure 6 .
Figure 6.Tested specimens and Main effects plot for tensile

Table 4 .
Percentage contribution of parameters in Tensile test

Table 5 .
Percentage contribution of parameters in Impact test

Table 6 .
Validation of Process parameters 5. Finally, from validation part we have predicted value of tensile test is 185.592N/mm² and practical value is about 186.889 N/mm² are approximately equal.The value of hardness test is 75.1 (BHN) and practical value is about 72.16 (BHN) are relatively equal and value of Impact test is 21.236 Joules and practical value is about 20 Joules are approximately equal.