# Examination of Friction Stir-Welded AA 6262/5456 Joints through the Optimization Technique

Authors: S. Vijayakumar; Selvaraj Manickam; Suresh Seetharaman; T.V.Janardhana Rao; Devabalan Pounraj; Hari Prasadarao Pydi
Journal: Advances in Materials Science and Engineering
 (2022)

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## Abstract

Friction stir welding (FSW) is the solid state welding technique which is mostly utilized to join similar and dissimilar Al, Cu, Mg, and their alloys. This research investigated that the tensile strength of FSW dissimilar Al6262 and Al5456 of 4 mm thickness is carried out using an H-13 tool pin along with different process variables such as tool rotational speed (TRS), welding speed (WS), and tool tilt angle (TTA). The selected parameters are set as TRS of 900, 1100, and 1400 rpm, WS of 20, 30, and 40 mm/min with TTA of 2, 2.5, and 3° to find out significant parameters on tensile strength (TS). The Taguchi L27 method is taken to create a number of experiments to recognize the optimal level of each parameter to accomplish the highest TS value. From the experimental results witnessed, the extreme TS (202.44 MPa) is acquired at sample 22 when maintaining TRS-1400 rpm, WS-30 mm/min, and TTA-2 degree, whereas minimum TS (165.88 MPa) is attained at sample 15 of TRS-1100 rpm, WS-30 mm/min, and TTA-3 degree. The ANOVA outcome revealed that TRS is the most significant factor (23.24%) which improves the tensile property of joints, followed by a weld speed of 21.7% and a combination of tool speed and weld speed (16.17%). The increment in the tool tilt angle does not play a vital role in improving the TS value, and MINITAB -17 software helped to find a relation between the parameters in the regression equation.


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## Body

## 1. Introduction

Aluminum alloys such as AA 6262 and 5456 are broadly employed in automotive, defense, and aerospace industries due to their high strength-to-weight ratio [1]. Nowadays, making fusion welding along with more mechanical properties and high corrosion resistance on aluminum alloys is a big problem in the industry. FSW has emerged as a potential replacement for traditional fusion welding techniques. This method is useful which connects a dissimilar metal’s surface by inserting a rotating pin tool into the metallic plates, and many research works have been performed to improve the tensile strength and other mechanical behavior of joint materials. M. R. Jandaghi et al. studied about mechanical properties of Al2198/7475 welded together by FSW; welded pieces were under solution treated at 480–540°C for about 90 minutes. Hardness (BHN) examination outcomes revealed that BHN values were increased in the Al7475 alloy portion while reducing at Al2198 [2]. Ravikumar explained the effect of input factors of FSW to join Al 6061with 7075 alloys. Three sorts of pin tools with different shapes such as cylinder, square, and tapered square were used [3]. Alavi and Tavassolimanesh demonstrated a novel method for producing bimetallic tubes. Using the FSW approach, they created bitubes out of copper and aluminum alloy. They also discovered that joint strength had dropped by an increment in tool speed [4]. Al alloy (2A70) was welded by gap adjustment between plates at different weld speeds. Tensile strength was increased up to 400 Mpa when we maintained a weld speed of around 180 mm/min [5]. Qi Song et al. investigated about how to improve the quality of FSW AZ-31B Mg/6061-T6 alloys by the RBFNN-GWO technique. The ultrasonic-type shoulder has been utilized as a weapon to make joints, and they established optimized parameters for weld speed (60 mm/min), rotating speed (915 rpm), and ultrasonic power (1485 W), which improved UTS by around 158 N/mm2 [6]. D. Maneiah conducted the research on FSW 6061-T6 Al alloys, three input factors are selected to find the optimal tensile strength (TS), and the outcomes discovered that maximum elongation (10%) and TS (190 Mpa) were attained at a tool rotating speed of 1400 rpm, 0 degree of the tilt angle, and 110 mm/min of the feed rate [7]. V. Preethi used bagasse ash as reinforcement (4–12% wt) and input parameter on welding operation along with tool speed and weld speed. L9 (OA) Taguchi design was considered for experimental works. Optimization results exposed that tool speed had the first main factor (53%) to improve the hardness of weld nuggets [8]. P. Cavaliere analyzed the mechanical behavior of AA2618 sheets/alumina produced via FSW; tensile test was carried out at high temperatures after T6 heat treatment. He found that joint sheets can withstand up to 500°C while performing tensile tests. The fracture surface was examined by using the scanning electron microscope (SEM) [9]. Devaraju Aruri produced Al6061-T6/SiC/alumina via the friction stir process and showed good hardness (BHN) when compared to base metal (6061) and also due to the presence of particles of silicon carbide and alumina that increases avoid distance of dislocation during deformation as well as decreasing elongation [10]. Sometimes, the microstructure grain size of the Ti-tube joint is affected by the increment of tool rotational speed. Khodir et al. concentrated on the microstructure of AA2024-T3/AA7075-T6, BHN, and tensile properties of the welded joints were examined by the influence of welding speed on the fixed location of base metals [11]. Hua-Bin Chen et al. studied about FSW of 5456 aluminum alloy under various conditions. Due to the small tilt angle of the tool (less than 1.5°), the plastic material could not flow adequately and had been driven down near the end of the pin during welding, weld flash was generated on the retreated side, and no sufficient plastic material fill-up in the nugget zone was noticed due to increase of tilt angle of more than 4.5° [12]. The weld strength, quality, heat generation, and material mixing are depending on parameters such as diameter and profile of the shoulder, length and diameter of the pin, tool angle, rotational speed, feed rate, and weld speed [13, 14]. The material under the shoulder pin is plasticized and moved along the joint line. The heat flux is produced by the combined frictional forces of the revolving shoulder pin along with the proper tilt angle and the applied forge force. In this context, the proper selection of parameters becomes a critical part in optimizing the FSW process [15, 16]. Heat generation and dissipation are mostly controlled by variation of speeds in welding and rotation and revealed that increasing the rotational speed and decreasing the welding speed reduce hardness values in the stir zone of AA7075-O and AA2024-T4 joints [17]. The shoulder diameter of the pin significantly disturbs the heat generated during the FSW process, and many researchers have discussed the effect of shoulder and pin diameter to produce better mechanical properties [18–20]. Rajkumer et al. investigated the effect of tool shoulder diameters on the tensile strength of AA1100 joints and decided that the joint with shoulder diameter (15 mm), tool rotational speed (900 rpm), and welding speed (100 mm/min) provided the higher tensile strength while comparing with other joints [21]. The ratio of shoulder diameter (D) and pin diameter (d) also affected the mechanical properties of FSW joints. For example, Vijayavel et al. studied the D/d ratio on tensile strength of LM25AA-5% SiC composite, revealing that a ratio of 3 provided the higher value of tensile strength [22]. Many researchers chose different processing factors to conduct their research to develop material and mechanical properties [23]. Some of the literature surveys played a main role to help us comprehend the selection of parameters in the friction stir-welding process. According to the above literature surveys, it was observed that only few articles discussed the influence of weld speed and tool tilt angle to join dissimilar Al alloys. Normally, the strength and quality of a weld depend on the heat generated and material mixing during weld operation as tool rotational speed, tilt angle, and weld speed are the most responsible factors to generate heat. It is also important to study the effect of those parameters in detail for joining Al6262 and Al5456 alloys by the FSW method and investigate the mechanical properties. Therefore, as per the Taguchi technique [24], we prepared 27 samples of joints by varying process factors, established statistical connections amongst the selected range of variables, and found the optimal tensile strength of Al 6262/5456 alloys. The preparation of FSW of Al5456/6262 is used in many applications including the manufacture of pressure vessels, screw machine products, nuts, oil line fittings, and valve parts.


## 2. Experimental Process

### 2.1. Material Selection and Methodology

The dissimilar Al6262 and Al5456 alloy plates are selected to be joined through the FSW approach, which possess the dimension of 100 mm∗60 mm ∗ 4 mm. The chemical element compositions and mechanical properties of both alloys are presented in Table 1 and Table 2, respectively. FSW joints are executed in both dissimilar metals by engaging in the HSS-13 tool, which has a Ǿ20 mm shoulder, 3.7 mm pin length, and Ǿ3 mm pin displayed in Figure 1. The ranges of each weld process factor TRS, WS, and TTA [25] are mentioned in Table 3.Table 1
Chemical composition Al6262 and Al5456 alloys (in wt.%).
MaterialMnFeMgSiZnTiCrCuBiPbAlAl62620.150.71.20.80.250.150.140.150.40.7BalanceAl54561.50.455.70.30.30.50.250.12——BalanceTable 2
Mechanical properties of Al6262 and Al5456.
MaterialTensile strength, TS (MPa)Yield strength, YS (MPa)Elongation,δ (%)Hardness (HV)Al62622602061285Al545630524415110Figure 1
FSW HSS-13 tool.Table 3
FSW process parameter levels.
LevelsTool rotational speed, TRS (rpm)Welding speed, WS (mm/min)Tool tilt angle, TTA (θ)190020221100302.531400403The special attachment with the milling machine is preferred to carryout welding operations. Before starting the operation, the grooves are created at the end of both Al plates 6262/5456, and they are tightly fitted over the table with clamps. The spinning tool is smoothly pierced into the specimens until the shoulder reaches 0.4 mm into the sample. To create the necessary heat for the procedure, the indicated location is fixed for 60–90 seconds [26, 27]. The tool then automatically passes the moving direction, as seen in Figure 2. The material enters the plastic phase due to formation of heat in the weld region and stirs because of tool movement, allowing both metals to combine together. The arrangement of the machine is removed after the weld is completed. Welding processes have been done with variations of FSW factors. RSM is an optimization strategy for analyzing experiment protocols, mathematical approaches, and statistical assumptions that allow for an empirical investigation of the system or process. Taguchi’s approach was to build models and scientific connections and examine the impact of input parameters on the output response of TS using Minitab-18 software.Figure 2
Tool and plate arrangements during the FSW process.


### 2.2. Tensile Test

The tensile samples are removed from the FSW process of Al composites as per the ASTM-E8 standard dimension with the help of a wire-cut electrical discharge machine. The schematic drawing of the tensile specimen is displayed in Figure3, and the tensile tests for all specimens are carried out by a servo-controlled universal machine, and some of the fracture specimens are shown in Figure 4.Figure 3
Schematic representation of the tensile sample.Figure 4
Fractured sample in the tensile test.A50 Gauge Length Extensometer is the equipment used for measuring the elongation of a specimen in a tensile test. This equipment clamps directly on the specimen as shown in Figure5. The clamping force is adjusted to control the pressure exerted on the specimen. A thumbscrew ensures accurate gauge length adjustment ranging from 12 mm to 51 mm. It is able to measure specimens that are 8 mm in thickness and 16 mm in width.Figure 5
Extensometer with A50 mm gauge length.


### 2.3. Welding Efficiency

The efficiency of FSW on TS is calculated with the standard value of TS of base materials (Al5456 &Al6262). The formula of the efficiency is shown asfd1(1)WeldEfficiency%=TSofweldsampleTSofBasematerial∗100.


## 2.1. Material Selection and Methodology

The dissimilar Al6262 and Al5456 alloy plates are selected to be joined through the FSW approach, which possess the dimension of 100 mm∗60 mm ∗ 4 mm. The chemical element compositions and mechanical properties of both alloys are presented in Table 1 and Table 2, respectively. FSW joints are executed in both dissimilar metals by engaging in the HSS-13 tool, which has a Ǿ20 mm shoulder, 3.7 mm pin length, and Ǿ3 mm pin displayed in Figure 1. The ranges of each weld process factor TRS, WS, and TTA [25] are mentioned in Table 3.Table 1
Chemical composition Al6262 and Al5456 alloys (in wt.%).
MaterialMnFeMgSiZnTiCrCuBiPbAlAl62620.150.71.20.80.250.150.140.150.40.7BalanceAl54561.50.455.70.30.30.50.250.12——BalanceTable 2
Mechanical properties of Al6262 and Al5456.
MaterialTensile strength, TS (MPa)Yield strength, YS (MPa)Elongation,δ (%)Hardness (HV)Al62622602061285Al545630524415110Figure 1
FSW HSS-13 tool.Table 3
FSW process parameter levels.
LevelsTool rotational speed, TRS (rpm)Welding speed, WS (mm/min)Tool tilt angle, TTA (θ)190020221100302.531400403The special attachment with the milling machine is preferred to carryout welding operations. Before starting the operation, the grooves are created at the end of both Al plates 6262/5456, and they are tightly fitted over the table with clamps. The spinning tool is smoothly pierced into the specimens until the shoulder reaches 0.4 mm into the sample. To create the necessary heat for the procedure, the indicated location is fixed for 60–90 seconds [26, 27]. The tool then automatically passes the moving direction, as seen in Figure 2. The material enters the plastic phase due to formation of heat in the weld region and stirs because of tool movement, allowing both metals to combine together. The arrangement of the machine is removed after the weld is completed. Welding processes have been done with variations of FSW factors. RSM is an optimization strategy for analyzing experiment protocols, mathematical approaches, and statistical assumptions that allow for an empirical investigation of the system or process. Taguchi’s approach was to build models and scientific connections and examine the impact of input parameters on the output response of TS using Minitab-18 software.Figure 2
Tool and plate arrangements during the FSW process.


## 2.2. Tensile Test

The tensile samples are removed from the FSW process of Al composites as per the ASTM-E8 standard dimension with the help of a wire-cut electrical discharge machine. The schematic drawing of the tensile specimen is displayed in Figure3, and the tensile tests for all specimens are carried out by a servo-controlled universal machine, and some of the fracture specimens are shown in Figure 4.Figure 3
Schematic representation of the tensile sample.Figure 4
Fractured sample in the tensile test.A50 Gauge Length Extensometer is the equipment used for measuring the elongation of a specimen in a tensile test. This equipment clamps directly on the specimen as shown in Figure5. The clamping force is adjusted to control the pressure exerted on the specimen. A thumbscrew ensures accurate gauge length adjustment ranging from 12 mm to 51 mm. It is able to measure specimens that are 8 mm in thickness and 16 mm in width.Figure 5
Extensometer with A50 mm gauge length.


## 2.3. Welding Efficiency

The efficiency of FSW on TS is calculated with the standard value of TS of base materials (Al5456 &Al6262). The formula of the efficiency is shown asfd1(1)WeldEfficiency%=TSofweldsampleTSofBasematerial∗100.


## 3. Results and Discussion

### 3.1. Influence of TRS on Tensile Strength

First Nine (L1-L9) samples are prepared by keeping TRS (900 rpm) constant and varying the WS and TTA from 20 to 40 mm/min and TTA 2 to 3°, respectively, in Figure6. It showed that a higher TS = 197.84 MPa was attained when maintaining WS (30 mm/min) and TTA (2.5°), whereas we found the least TS (179.38 Mpa) at WS-30 mm/min and TTA- 2°. The second nine samples (L10-18) were made by increasing the TRS level from 900 to 1100 rpm. It was noticed that tensile strength maximum (196.89 Mpa) at sample 16 and minimum (165.88 MPa) at sample L15 were achieved due to increasing of weld speed from 30 to 40 mm/min and decreasing of tilt angle 3 to 2° in Figure 7. The final 9 samples (L19-27) were produced by the change of tool speed at 1400 rpm, and Figure 8 noticed that higher (202.44 MPa) and low values (174.88 MPa) were acquired in sample L22 (WS-30 mm/min and TTA-2 deg) and sample L19 (WS-20 mm/min and TTA-2 deg) correspondingly.Figure 6
Influence of TRS -900 rpm on TS.Figure 7
Influence of TRS -1100 rpm on TS.Figure 8
Influence of TRS -1400 rpm on TS.The complete experimental results are mentioned in Table4. Amongst 27 welded samples (Figure 9), extreme and last optimal groupings of FSW factors at output response TS are recognized in samples L22 and L15 in which collective parameter levels are TRS3-WS2-TTA1 (1400 rpm, 30 mm/min, and 2°) and TRS2-WS2-TTA3 (1100 rpm, 30 mm/min, and 3°). As per the collection of results, TS is directly proportional to the welding speed up to 30 mm/min. With a higher welding speed, flaws such as voids have a detrimental impact on tensile strength and precipitates, and grain sizes are also most important to vary the TS value [28]. When WS and TRS reached 40 mm/minute and 1400 rpm, a deformation mismatch in the joint is caused by a discontinuous void caused by inadequate material mixing. The maximum and minimum TS values are attained on the prepared samples L22 and L15, respectively. Those samples are displayed in Figures 10 and 11. Some of the defects such as voids, excessive flash, porosity, and groove are found due to depth of the pin. The plastic material close to the pin was extruded when the pin plug depth was deep, which led to weld flash. When the depth of the pin plug is inadequate, a void and flash defect will develop on the weld surface (Figure 11). The weld joint efficiency of each aluminum composite is shown in Table 5. The percentage of FSW efficiency is more while comparing with Al5456 but less with Al6262.Table 4
Experimental observations.
Welded samplesTRS (rpm)WS (mm/min)TTA (degree)TS (MPa)L1900202192.65L2900202.5193.28L3900203189.54L4900302179.38L5900302.5197.84L6900303187.92L7900402195.68L8900402.5194.77L9900403196.27L101100202175.53L111100202.5186.64L121100203169.29L131100302170.58L141100302.5171.29L151100303165.88L161100402196.89L171100402.5195.76L181100403189.79L191400202174.88L201400202.5199.26L211400203186.84L221400302202.44L231400302.5183.52L241400303179.29L251400402181.99L261400402.5195.37L271400403193.78Figure 9
Overall tensile strength results.Figure 10
Maximum tensile strength attained at L22 sample.Figure 11
Minimum tensile strength attained at L15 sample.Table 5
Welding efficiency-tensile strength.
Al5456/Al6262 FSW samplesTensile strength (MPa)Weld joint efficiency with Al5456 (A/B) x 100 in (%)Weld joint efficiency with Al5456 (in (%)) (A/C) x 100 in (%)Al5456/Al6262 composites (A)Al5456 alloy (B)Al6262 alloy (C)L1192.6530526063.1639374.09615L2193.2830526063.3704974.33846L3189.5430526062.1442672.9L4179.3830526058.8131168.99231L5197.8430526064.8655776.09231L6187.9230526061.6131172.27692L7195.6830526064.1573875.26154L8194.7730526063.8590274.91154L9196.2730526064.3508275.48846L10175.5330526057.5508267.51154L11186.6430526061.1934471.78462L12169.2930526055.5049265.11154L13170.5830526055.9278765.60769L14171.2930526056.1606665.88077L15165.8830526054.3868963.8L16196.8930526064.554175.72692L17195.7630526064.1836175.29231L18189.7930526062.2262372.99615L19174.8830526057.337767.26154L20199.2630526065.3311576.63846L21186.8430526061.2590271.86154L22202.4430526066.3737777.86154L23183.5230526060.1704970.58462L24179.2930526058.7836168.95769L25181.9930526059.6688569.99615L26195.3730526064.0557475.14231L27193.7830526063.5344374.53077


## 3.1. Influence of TRS on Tensile Strength

First Nine (L1-L9) samples are prepared by keeping TRS (900 rpm) constant and varying the WS and TTA from 20 to 40 mm/min and TTA 2 to 3°, respectively, in Figure6. It showed that a higher TS = 197.84 MPa was attained when maintaining WS (30 mm/min) and TTA (2.5°), whereas we found the least TS (179.38 Mpa) at WS-30 mm/min and TTA- 2°. The second nine samples (L10-18) were made by increasing the TRS level from 900 to 1100 rpm. It was noticed that tensile strength maximum (196.89 Mpa) at sample 16 and minimum (165.88 MPa) at sample L15 were achieved due to increasing of weld speed from 30 to 40 mm/min and decreasing of tilt angle 3 to 2° in Figure 7. The final 9 samples (L19-27) were produced by the change of tool speed at 1400 rpm, and Figure 8 noticed that higher (202.44 MPa) and low values (174.88 MPa) were acquired in sample L22 (WS-30 mm/min and TTA-2 deg) and sample L19 (WS-20 mm/min and TTA-2 deg) correspondingly.Figure 6
Influence of TRS -900 rpm on TS.Figure 7
Influence of TRS -1100 rpm on TS.Figure 8
Influence of TRS -1400 rpm on TS.The complete experimental results are mentioned in Table4. Amongst 27 welded samples (Figure 9), extreme and last optimal groupings of FSW factors at output response TS are recognized in samples L22 and L15 in which collective parameter levels are TRS3-WS2-TTA1 (1400 rpm, 30 mm/min, and 2°) and TRS2-WS2-TTA3 (1100 rpm, 30 mm/min, and 3°). As per the collection of results, TS is directly proportional to the welding speed up to 30 mm/min. With a higher welding speed, flaws such as voids have a detrimental impact on tensile strength and precipitates, and grain sizes are also most important to vary the TS value [28]. When WS and TRS reached 40 mm/minute and 1400 rpm, a deformation mismatch in the joint is caused by a discontinuous void caused by inadequate material mixing. The maximum and minimum TS values are attained on the prepared samples L22 and L15, respectively. Those samples are displayed in Figures 10 and 11. Some of the defects such as voids, excessive flash, porosity, and groove are found due to depth of the pin. The plastic material close to the pin was extruded when the pin plug depth was deep, which led to weld flash. When the depth of the pin plug is inadequate, a void and flash defect will develop on the weld surface (Figure 11). The weld joint efficiency of each aluminum composite is shown in Table 5. The percentage of FSW efficiency is more while comparing with Al5456 but less with Al6262.Table 4
Experimental observations.
Welded samplesTRS (rpm)WS (mm/min)TTA (degree)TS (MPa)L1900202192.65L2900202.5193.28L3900203189.54L4900302179.38L5900302.5197.84L6900303187.92L7900402195.68L8900402.5194.77L9900403196.27L101100202175.53L111100202.5186.64L121100203169.29L131100302170.58L141100302.5171.29L151100303165.88L161100402196.89L171100402.5195.76L181100403189.79L191400202174.88L201400202.5199.26L211400203186.84L221400302202.44L231400302.5183.52L241400303179.29L251400402181.99L261400402.5195.37L271400403193.78Figure 9
Overall tensile strength results.Figure 10
Maximum tensile strength attained at L22 sample.Figure 11
Minimum tensile strength attained at L15 sample.Table 5
Welding efficiency-tensile strength.
Al5456/Al6262 FSW samplesTensile strength (MPa)Weld joint efficiency with Al5456 (A/B) x 100 in (%)Weld joint efficiency with Al5456 (in (%)) (A/C) x 100 in (%)Al5456/Al6262 composites (A)Al5456 alloy (B)Al6262 alloy (C)L1192.6530526063.1639374.09615L2193.2830526063.3704974.33846L3189.5430526062.1442672.9L4179.3830526058.8131168.99231L5197.8430526064.8655776.09231L6187.9230526061.6131172.27692L7195.6830526064.1573875.26154L8194.7730526063.8590274.91154L9196.2730526064.3508275.48846L10175.5330526057.5508267.51154L11186.6430526061.1934471.78462L12169.2930526055.5049265.11154L13170.5830526055.9278765.60769L14171.2930526056.1606665.88077L15165.8830526054.3868963.8L16196.8930526064.554175.72692L17195.7630526064.1836175.29231L18189.7930526062.2262372.99615L19174.8830526057.337767.26154L20199.2630526065.3311576.63846L21186.8430526061.2590271.86154L22202.4430526066.3737777.86154L23183.5230526060.1704970.58462L24179.2930526058.7836168.95769L25181.9930526059.6688569.99615L26195.3730526064.0557475.14231L27193.7830526063.5344374.53077


## 4. Optical Microscope

The optical microscopic images of the dissimilar friction stir-welded Al alloy for sample no: L22 at 200X magnification are shown in Figure12. Figures 12(a) and 12(b) show the microstructure of Al5456 and 6262. It is perceived that the huge number of dark spots and the presence of a huge quantity of strengthening precipitate in Figure 12(a). The grains of Al6262 are oriented along the rolling direction of the plates in Figure 12(b); it is marked that the grains are rougher in the HAZ region when compared to the Al5456 base metal in Figure 12(c). From Figure 12(d), we witnessed that the grain development and Mg2Si precipitate amount in the HAZ -Al6262 are reduced. Figure 12(e) displays the grains are shattered down into finer grain sizes in the weld nuggets because of the mixing of two dissimilar Al alloys.Figure 12
Optical microstructure image of the L22 specimen. (a) Al5456 base metal. (b) Al6262 base metal. (c) HAZ in Al5456. (d) HAZ in Al6262. (e) Weld nugget.
(a)(b)(c)(d)(e)


### 4.1. Regression Analysis in the Taguchi Method

Taguchi optimized, and ANOVA is used to improve process variables in order to achieve the specified weld joint strength at a 95% level of confidence [25]. The SN ratio table is produced from experimental readings and considered that “Minimum is best,” and its readings are listed in Table 6. The means of TS and the maximum-to-maximum delta values are specified as ranks 1, 2, and 3 correspondingly. TRS, WS, and TTA are ranked as 1st, 2nd, and 3rd positions, respectively. Optimum TS was perceived at the last level of TRS (191.9 MPa) as Ist rank, 3rd level of WS (193.4 MPa) as 2nd rank, and 2nd level of TTA (190.9 Mpa) as 3rd rank in Table 7 and Figure 13.Table 6
SN ratio outcomes.
LevelTRSWSTTA1−45.66−45.35−45.352−45.10−45.18−45.613−45.50−45.73−45.30Delta0.560.540.31Rank123Table 7
Means response (TS).
LevelTRSWSTTA1191.9185.3185.62180.2182.0190.93188.6193.4184.3Delta11.711.46.6Rank123Figure 13
Tensile strength means plot.In the Taguchi technique, both F andP values are an imperative part of detecting the predictability of selected quadratic regression of the model; ANOVA was carried out thoroughly for analysis of the significance of the model. If P is more than 0.05, the selected factors should be considered insignificant and less than 0.05 which may be considered influenced variables [29]. The contribution of each and the combination parameters on ANOVA outcomes have been calculated in which TRS and WS are the most contributed variables that improve the tensile strength of welded samples because it is the satisfying condition of the regression model (P<0.05) in the optimization process. It was noticed that tool rotational speed (TRS) is the best contribution variable (23.24%), followed by weld speed (WS) about 21.7%, and combined parameters (TRS∗WS) of around 16.17%. Apart from these, the involvement of TTA and combination of TRS/TTA and WS/TTA are very less to contribute extra strength to weld joints in Table 8. The forecast regression equation of TS was attained from optimal software (MINITAB-17) which is presented as follows . It explains the relationship between the process parameters of TRS, WS, and TTA and finds out predicted values of tensile strength in the equationfd2.(2)TS=182.4−0.00392TRS+0.402WS−1.27TTA.Table 8
Analysis of variance response (TS).
Welding factorsD.FSSMSFPContribution (%)TRS2659.24329.624.010.04223.24WS2613.45306.733.730.05221.7TTA2218.63109.321.330.3177.7TRS∗WS4452.64113.161.380.32416.17TRS∗TTA455.5613.890.170.9481.9WS∗TTA4157.2739.320.480.7515.5Residual error8657.2782.1623.05Total262814.06Figure14 portrays the influence of tool speed and weld speed on the response of tensile strength. The blue region indicated a lower TS value, while dark green projected the maximum TS. It is identified that the strength of welds is improved by increasing TRS (1000 to 1400 rpm) and WS (25 to 40 mm/min). Similarly, the influence of TRS and TTA together was shown in Figure 15 in which the TS value was reduced even though increasing TTA from 2.5 to 3° which means tensile strength is indirectly proportional to tool tilt angle but is directly proportionate to TRS. Figure 16 revealed the effect of WS and TTA on TS. It exposed that the raise of WS and decrement in TTA led to improvement in the tensile properties of joints.Figure 14
Contour plot TS vs TRS and WS.Figure 15
Contour plot TS vs TRS and TTA.Figure 16
Contour plot TS vs WS and TTA.


## 4.1. Regression Analysis in the Taguchi Method

Taguchi optimized, and ANOVA is used to improve process variables in order to achieve the specified weld joint strength at a 95% level of confidence [25]. The SN ratio table is produced from experimental readings and considered that “Minimum is best,” and its readings are listed in Table 6. The means of TS and the maximum-to-maximum delta values are specified as ranks 1, 2, and 3 correspondingly. TRS, WS, and TTA are ranked as 1st, 2nd, and 3rd positions, respectively. Optimum TS was perceived at the last level of TRS (191.9 MPa) as Ist rank, 3rd level of WS (193.4 MPa) as 2nd rank, and 2nd level of TTA (190.9 Mpa) as 3rd rank in Table 7 and Figure 13.Table 6
SN ratio outcomes.
LevelTRSWSTTA1−45.66−45.35−45.352−45.10−45.18−45.613−45.50−45.73−45.30Delta0.560.540.31Rank123Table 7
Means response (TS).
LevelTRSWSTTA1191.9185.3185.62180.2182.0190.93188.6193.4184.3Delta11.711.46.6Rank123Figure 13
Tensile strength means plot.In the Taguchi technique, both F andP values are an imperative part of detecting the predictability of selected quadratic regression of the model; ANOVA was carried out thoroughly for analysis of the significance of the model. If P is more than 0.05, the selected factors should be considered insignificant and less than 0.05 which may be considered influenced variables [29]. The contribution of each and the combination parameters on ANOVA outcomes have been calculated in which TRS and WS are the most contributed variables that improve the tensile strength of welded samples because it is the satisfying condition of the regression model (P<0.05) in the optimization process. It was noticed that tool rotational speed (TRS) is the best contribution variable (23.24%), followed by weld speed (WS) about 21.7%, and combined parameters (TRS∗WS) of around 16.17%. Apart from these, the involvement of TTA and combination of TRS/TTA and WS/TTA are very less to contribute extra strength to weld joints in Table 8. The forecast regression equation of TS was attained from optimal software (MINITAB-17) which is presented as follows . It explains the relationship between the process parameters of TRS, WS, and TTA and finds out predicted values of tensile strength in the equationfd2.(2)TS=182.4−0.00392TRS+0.402WS−1.27TTA.Table 8
Analysis of variance response (TS).
Welding factorsD.FSSMSFPContribution (%)TRS2659.24329.624.010.04223.24WS2613.45306.733.730.05221.7TTA2218.63109.321.330.3177.7TRS∗WS4452.64113.161.380.32416.17TRS∗TTA455.5613.890.170.9481.9WS∗TTA4157.2739.320.480.7515.5Residual error8657.2782.1623.05Total262814.06Figure14 portrays the influence of tool speed and weld speed on the response of tensile strength. The blue region indicated a lower TS value, while dark green projected the maximum TS. It is identified that the strength of welds is improved by increasing TRS (1000 to 1400 rpm) and WS (25 to 40 mm/min). Similarly, the influence of TRS and TTA together was shown in Figure 15 in which the TS value was reduced even though increasing TTA from 2.5 to 3° which means tensile strength is indirectly proportional to tool tilt angle but is directly proportionate to TRS. Figure 16 revealed the effect of WS and TTA on TS. It exposed that the raise of WS and decrement in TTA led to improvement in the tensile properties of joints.Figure 14
Contour plot TS vs TRS and WS.Figure 15
Contour plot TS vs TRS and TTA.Figure 16
Contour plot TS vs WS and TTA.


## 5. Conclusion

In this work, aluminum alloy 6262/5456 are welded together with the aid of a pin tool and different FSW process considerations such as tool rotational speed (TRS), weld speed (WS), and tool tilt angle (TTA). This current research’s aim is to develop the tensile strength of fused joints by influence of FSW parameters. As per the Taguchi L27 orthogonal array, twenty seven welded samples are produced, and we conduct a tensile test on each sample. The following results are found:(i)
According to contour plots and mean plots of TS, when increasing weld speed and tool speed, TS values are increased(ii)
Increase of tool tilt angle reduces tensile property(iii)
The highest amount of TS = 202.44 MPa is achieved in sample 22 when retaining TRS of 1400 rpm, WS of 30 mm/min, and 2°, and the lowest amount is attained at sample 15 due to maintaining less tool speed of 1100 rpm, 30 mm/min of weld speed, and increasing the tool tilt angle of 3°(iv)
From ANOVA and response table of TS in optimization software, we identified that TRS is the major parameter which is contributing around 24% to develop tensile property, trailed by WS at 21.7%, and the combination of TRS∗WS about 16.2%, and the involvement of TTA is low about only 7%


## 6. Disclosure

It was performed as a part of the Employment Bule Hora University, Ethiopia.



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*Source: 4527595-2022-09-19.xml*