Experimental Investigation of the Friction Stir Weldability of AA8006 with Zirconia Particle Reinforcement and Optimized Process Parameters

materials

Article Experimental Investigation of the Friction Stir Weldability of AA8006 with Zirconia Particle Reinforcement and Optimized Process Parameters

Thanikodi Sathish 1,*, Abdul Razak R. Kaladgi 2 , V. Mohanavel 3,*, K. Arul 4 , Asif Afzal 2,* , Abdul Aabid 5 , Muneer Baig 5 and Bahaa Saleh 6

1 Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences (SIMATS), Chennai 602105, Tamil Nadu, India 2 Department of Mechanical Engineering, P.A. College of Engineering (Afﬁliated to Visvesvaraya Technological University, Belagavi), Mangaluru 574153, Karnataka, India; [email protected] 3 Centre for Materials Engineering and Regenerative Medicine, Bharath Institute of Higher Education and Research, Chennai 600073, Tamilnadu, India 4 Department of Mechanical Engineering, Jeppiaar SRR Engineering College, Chennai 603103, Tamilnadu, India; [email protected] 5 Engineering Management Department, College of Engineering, Prince Sultan University, P.O. Box 66833, Riyadh 11586, Saudi Arabia; [email protected] (A.A.); [email protected] (M.B.) 6 Mechanical Engineering Department, College of Engineering, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia; [email protected] * Correspondence: [email protected] (T.S.); [email protected] (V.M.); [email protected] (A.A.)

Citation: Sathish, T.; Kaladgi, A.R.R.; Abstract: A lightweight, highly corrosive resistant, and high-strength wrought alloy in the aluminum Mohanavel, V.; Arul, K.; Afzal, A.; family is the Aluminium 8006 alloy. The AA8006 alloy can be formed, welded, and adhesively Aabid, A.; Baig, M.; Saleh, B. Experimental Investigation of the bonded. However, the recommended welding methods such as laser, TIG (Tungsten Inert Gas Friction Stir Weldability of AA8006 welding), and ultrasonic are more costly. This investigation aims to reduce the cost of welding with Zirconia Particle Reinforcement without compromising joint quality by means of friction stir welding. The aluminum alloy-friendly and Optimized Process Parameters. reinforcement agent zirconia is utilized as particles during the weld to improve the performance Materials 2021, 14, 2782. https:// of the newly identiﬁed material AA8006 alloy in friction stir welding (FSW). The objectives of this doi.org/10.3390/ma14112782 research are to identify the level of process parameters for the friction stir welding of AA8006 to reduce the variability by the trial-and-error experimental method, thereby reducing the number of Academic Editors: Massimiliano samples needing to be characterized to optimize the process parameters. To enhance the quality of Avalle and Bolv Xiao the weld, the friction stir processing concept will be adapted with zirconia reinforcement during welding. The friction stir-processed samples were investigated regarding their mechanical properties Received: 13 April 2021 such as tensile strength and Vickers microhardness. The welded samples were included in the Accepted: 19 May 2021 corrosion testing to ensure that no foreign corrosive elements were included during the welding. The Published: 24 May 2021 quality of the weld was investigated in terms of its surface morphology, including aspects such as the

Publisher’s Note: MDPI stays neutral dispersion of reinforced particles on the welded area, the incorporation of foreign elements during with regard to jurisdictional claims in the weld, micro defects or damage, and other notable changes through scanning electron microscopy published maps and institutional affil- analysis. The process of 3D profilometry was employed to perform optical microscopy investigation iations. on the specimens inspected to ensure their surface quality and finish. Based on the outcomes, the optimal process parameters are suggested. Future directions for further investigation are highlighted.

Keywords: friction stir welding; AA8006 alloy; zirconia; SEM analysis; 3D proﬁlometry and

Copyright: © 2021 by the authors. wrought alloy Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons 1. Introduction Attribution (CC BY) license (https:// The solid-state welding method of Friction Stir Welding (FSW) is a newly modiﬁed creativecommons.org/licenses/by/ process. This process is effectively utilized for altering surface structures and improving 4.0/).

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materials’ physical properties. The term friction stir processing (FSP) refers to surface modification through reinforcements in addition to friction stir welding [1–10]. This research investigates the effects of the novel reinforcement of zirconia particles on the welding zone of the friction stir welding process of the AA8006 work material. Various research findings support the continuous improvement of this process and describe the effective welding of similar and dissimilar metals by friction stir welding. The term friction stir processing (FSP) refers to surface modification by means of reinforcement in addition to friction stir welding. Abhishek et al. [1] analyzed the joining of the AA 6061 alloy by FSP and utilized silicon carbide-graphite as a reinforcement to form a hybrid composite weld material, finding that the strength of the weld improved. The uniform dispersion of the reinforcement agent was ensured by microstructural investigation. It was reported that the stirring speed is a major influencing factor and is responsible for modifying the mechanical properties of hybrid composite welds. The use of a high rotational speed of 2200 rpm at 25 mm/min for traverse speed forms a strong weld. Kan et al. [2] recommends the use of FSP, as it develops a defect-free weld and can form a composite weld material at joints with excellent hardness and wear properties. It was found that though the tool pin was considered durable, it suffers from wear over time and such wear is unavoidable due to friction and heat while stirring. Such wear will increase the tool and welding cost. Apart from the use of aluminum metal matrix composite weld metal on aluminum welding joints, Palanivel et al. [3] introduced a hybrid Aluminium Matrix Composites (AMC) (reinforced with titanium boride boron nitride) composite weld material. This is titanium boride and boron nitride introduced as a tribo film form in the FSP of aluminum alloy 6082 on a welding zone to form a hybrid AMC composite weld material. It was found that TiB2 particles were broken and boron nitride particles were not broken on the weld material. This method can improve the wear resistance. Boron nitride reduces the debris in the wear caused by the iron content and could possibly also reduce the counter face wear. Harikrishna Rana and Vishvesh Badheka et al. [4] welded AA7075 work materials with boron carbide reinforcement using FSP and created an aluminum matrix composite weld material at the joint. The maximum stirring speed and frequently changes the traverse speed, producing more heat, it can be reduced the wear resistance. As tool pin profile is a major influencing factor, Saravanan et al. [5,6] optimized the tool pin profile to improve the welding quality. They utilized the FSW of the dissimilar aluminum alloys of AA 2014 and AA 7075. In their investigation, they made only three joints by varying the stirring speed of the tool pin, altering the fixed material’s situation at withdrawing as well as progressing sides, and achieved a maximum rigidity of 207 MPa. Pandiyarajanet al. [7] investigated the joining of AA6061 plates by FSP with zirconia reinforcement and ensured that the reinforcements showed a uniform distribution of ZrO2 on the weld material through Scanning Electron Microscopy (SEM) analysis; the hardness at the joints significantly improved. Sivaraman et al. [8] also investigated the development of the dissimilar metals AA 2014 and AA 7075 through friction stir welding. They altered the rotational speed and material position to obtain a better impact and tensile strength. Ramamoorthi et al. [9] analyzed the friction stir welding of the dissimilar metals, AA5086 and AA6063, by varying the axial force, and reported that axial force strongly influenc was the mechanical properties of the welded joints. Fakkir Mohamed et al. [10] also investigated the FSW of the dissimilar metals AA5083 and AA6061 by varying three important parameters: load, feed, and speed. The speed is a more influential parameter than the other two in producing a high standard of welding. Ref. [11] achieved a high UTS of 920 MPa with 37% elongation in the FSW of Al0.3CoCrCu0.3FeNi high-entropy alloy through the microstructure of the stir zone, which was partially re-crystallized and fine grained. This investigation utilized a novel approach toAA8006 welding by means of FSP with zirconia particle reinforcement. The aluminum alloy AA8006 is usually used in costly welding methods such as ultrasonic welding, laser welding, and Tungsten Inert Gas (TIG) welding. This investigation aims to reduce the cost of welding AA8006 without compromising the weld quality by FSP. Hence, this investigation is completely unique, as we attempt to use new techniques to increase Materials 2021, 14, 2782 3 of 15

the applications of AA8006. It is important to investigate this material because, compared to other aluminum alloys, the 8006 alloy possesses superior corrosion resistance and high strength. It is a category of wrought alloys that can be treated thermo-mechanically to improve their strength.

2. Materials and Methods 2.1. Base Material Aluminium 8006 alloy is a high-strength (elastic modulus 70MPa) and highly corrosive resistant alloy. It is often referred as a wrought alloy. The AA 8006 was named a medium- strength alloy; it is used in many different applications, such as in making containers, heat exchanger units, tin boxes, and cable covers, etc. This material has a great formability, with a good mechanical strength. The constituents of the AA8006 alloy are presented in Table1.

Table 1. Constituents of the AA8006 alloy.

Name of the Constituent in AA8006 Alloy Chemical Symbol Percentage of Contribution Zinc Zn 0.75% Magnesium Mg 0.69% Copper Cu 0.27% Silicon Si 0.36% Iron Fe 1.60% Manganese Mn 0.58% Aluminum Al 95.60% Other Elements Each - 0.04% Total Sum of Others - 0.11%

2.2. Reinforcement Agent In this study, the AA8006 aluminum alloy is taken as a base alloy and the packing of reinforced material such as zirconia and the fabrication can be carried out by the use of FSP technology. The reinforcement of zirconium dioxide is preferred, as it possesses an excellent stability against mechanical stresses and is resistant to cracking and crack growth. Apart from its high ﬂexural strength (up to 1000 MPa), it has a fracture toughness of 10 MPa M1/2 at 20 ◦C, a tensile strength of 30 Mpa, and an elastic modulus of up to 250 GPa. Zirconia is an inorganic metal oxide that can act as a successful reinforcement material for the property enhancement of aluminum alloys. It has proven inclusion effects in many aluminum metal matrix composites as well as in FSP. Zirconia is mainly utilized in the reinforcement of ceramic materials; it is mainly applied in the production of abrasive parts, dental applications, and fuel cells [7].

2.3. Experimentation As described above, the number of process variables was reduced by trial-and-error experiments, because to our best knowledge no previous work on AA8006 has been reported so far in the literature. Therefore, the weldability was justiﬁed by trial-and- error experimentations. To enhance the quality of the weld, the friction stirs processing concept was adapted with zirconia reinforcement at the weld. We utilized 6 mm-thick, 150 × 75 mm rectangular-shaped samples plates for FSP. The American Society for Testing Materials ASTM D638 standard was adhered to and a computer-controlled 100 KN capacity Universal Testing Machine (model: SICMUTM-01, manufacturer: Shambhavi, city: Navi, state: Mumbai) was employed in this investigation [12–15]. FSP is a novel route developed from the origin of the FSW process, the reinforcement tactic used to modify the surface microstructure of the material while in FSP. Table2 shows the different ranges of tool pin speed, traverse speed, tool downward force, and tool tilt angle. Five samples in each experimental group (stirring speed setting) were investigated and the average of their values were considered for evaluation and in drawing conclusions. Materials 2021, 14, x FOR PEER REVIEW 4 of 17

FSP is a novel route developed from the origin of the FSW process, the reinforcement tactic used to modify the surface microstructure of the material while in FSP. Table 2 shows the different ranges of tool pin speed, traverse speed, tool downward force, and tool tilt angle. Five samples in each experimental group (stirring speed setting) were investigated and the average of their values were considered for evaluation and in drawing Materials 2021, 14, 2782 conclusions. 4 of 15

Table 2. Description of theprocess parameters used for FSP.

Experi- Stirring (Tool Pin Rotational)Table 2. Description Traverse of theprocess Speed of parameters Tool Compressive used for FSP. Force on Tool Tilt Angle in mental. Speed (rpm) HeadStirring (mm per (Tool min) Pin Traverse SpeedTool of (kN) Compressive Degree Index. Experimental. Tool Tilt Angle in Rotational) Speed Tool Head (mm Force on Tool Index. Degree 1 800 40(rpm) per min) 3 (kN) 2 2 900 1 40 800 40 3 3 2 2 3 1000 2 40 900 40 3 3 2 2 3 1000 40 3 2 4 1100 4 40 1100 40 3 3 2 2

The designed tool shoulder and straight cylindrical tool pin are depicted in Figure 1. The designed tool shoulder and straight cylindrical tool pin are depicted in Figure1. Figure 1a shows a conceptual design of the FSP tool and compacting tool. Its dimensional Figure1a shows a conceptual design of the FSP tool and compacting tool. Its dimensional features are shown in Figure 1b and the actual fabricated tool is depicted in Figure 1c. features are shown in Figure1b and the actual fabricated tool is depicted in Figure1c. Tools Tools are utilized in a Computerized Numerical Control (CNC), (model: JV 30, manufac- are utilized in a Computerized Numerical Control (CNC), (model: JV 30, manufacturer: turer: Lakshmi Machine works, city: Coimbatore, state: Tamil Nadu) machine and the tool Lakshmi Machine works, city: Coimbatore, state: Tamil Nadu) machine and the tool is is made out of high-carbon high chromium steel. made out of high-carbon high chromium steel.

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(a) (b)

(c) 4 Figure 1. FSP tool: (a) compactingFigure and 1.FSPFSP tool tool: shape (a) compactingfeature; (b) dimensional and FSP tool feature shape feature;of FSP tool; (b) dimensional feature of FSP tool; (c) fabricated FSP tool. (c) fabricated FSP tool.

The base material of the AAThe 8006 base has material the dimensions of the AA of 8006 200×100×10 has the dimensions mm. The top of 200 × 100 × 10 mm. The top surface of the samples has asurface square ofgroove the samples depth of has 5mm a square and width groove of depth 3mm, of which 5 mm are and width of 3 mm, which are cut using the wire EDM process, as shown in Figure 2a. The next stage of the reinforced particles of zirconium dioxide is filling in the groove on the base material surface and tightly compressing them, as shown in Figure 2b.

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(c) Figure 1. FSP tool: (a) compacting and FSP tool shape feature; (b) dimensional feature of FSP tool; (c) fabricated FSP tool. Materials 2021, 14, 2782 5 of 15 The base material of the AA 8006 has the dimensions of 200×100×10 mm. The top surface of the samples has a square groove depth of 5mm and width of 3mm, which are cut using the wire EDM process, as shown in Figure 2a. The next stage of the reinforced particles ofcut zirconium using the dioxide wire EDM is filling process, in asthe shown groove in on Figure the 2basea. The material next stage surface of the and reinforced tightly compressingparticles of them, zirconium as shown dioxide in Figure is ﬁlling 2b. in the groove on the base material surface and tightly compressing them, as shown in Figure2b.

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Figure 2. FSP processFigure procedure: 2. FSP process (a) square procedure: groove (a on) square the base groove material; on the (b) base reinforced material; particles (b) reinforced particles filling in the groove;ﬁlling ( inc) thecompaction groove; (processc) compaction using a process pinless using tool; and a pinless (d) FSP tool; process. and (d ) FSP process.

The packing ofThe reinforced packing ofparticles reinforced in the particles groove in was the achieved groove was with achieved the help with of a the help of a pinless tool, aspinless shown tool, in Figure as shown 2c. A in CNC Figure vertical2c. A CNCmilling vertical machine milling was machineused to rotate was used the to rotate the pinless tool, pressingpinless tool, the particles pressing tightly the particles and closing tightly the and groove closing without the groove the reinforced without the reinforced particles escaping.particles The escaping. FSP process The was FSP carried process out was finally carried with out the ﬁnally assistance with the of a assistance straight of a straight cylindrical pin tool, as shown in Figure2d. The FSP process mixed the zirconium dioxide cylindrical pin tool, as shown in Figure 2d. The FSP process mixed the zirconium dioxide particles into base materials with a different tool rotational speed; due to the heat generation, particles into base materials with a different tool rotational speed; due to the heat genera- the particles are mixed well into base materials [15]. tion, the particles are mixed well into base materials [15].

2.4. Characterization for Tensile Strength of Welded Samples The upgrading of the surface structure by FSP increased the strength of the specimens to a maximum level. The four samples were tested to see if they met the ASTM E8M- 04 standard; the 40-ton capacity of Universal Testing Machine (UTM) was used, Figure 3 was illustrates to employed for conducting tensile strength testing on the samples. The strain rate was measured with the aid of an extensometer [16–18]. The four samples were tested at 1100 rpm. The FSP showed that, the sample tensile strength was moderately increased, proving that a higher tool rotational speed drastically modified the surface structure. The thickness of the specimen was 3 mm. The sample width and length were 25 and 240 mm, respectively. The specimen was loaded vertically along the loading direction and gripped. A uniform displacement of 0.02 cm per min was applied. The dimensions of the broken area were measured with a vernier caliper and the cross section was calculated.

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2.4. Characterization for Tensile Strength of Welded Samples The upgrading of the surface structure by FSP increased the strength of the specimens to a maximum level. The four samples were tested to see if they met the ASTM E8M-04 standard; the 40-ton capacity of Universal Testing Machine (UTM) was used, Figure3 was illustrates to employed for conducting tensile strength testing on the samples. The strain rate was measured with the aid of an extensometer [16–18]. The four samples were tested at 1100 rpm. The FSP showed that, the sample tensile strength was moderately increased, proving that a higher tool rotational speed drastically modiﬁed the surface structure. The thickness of the specimen was 3 mm. The sample width and length were 25 and 240 mm, respectively. The specimen was loaded vertically along the loading direction and gripped. Materials 2021, 14, x FOR PEER REVIEW 7 of 17 A uniform displacement of 0.02 cm per min was applied. The dimensions of the broken area were measured with a vernier caliper and the cross section was calculated.

FigureFigure 3. 3. ImageImage of of tensile tensile test test ( (aa)) before before fracture, fracture, ( (bb)) after after fracture. fracture.

2.5.2.5. Characterization Characterization for for Hardness Hardness of of Welded Welded Samples Samples InIn this this section, section, the the microhardness microhardness of of th thee specimens at at various locations from from the welded zone is analyzed. We examined how the microhardness varied from the center of welded zone is analyzed. We examined how the microhardness varied from the center of the weld with respect to a uniform distance to the extreme edges of the plate. The FSP the weld with respect to a uniform distance to the extreme edges of the plate. The FSP zone was the center of the weld, the thermo-mechanically affected zone was the portion zone was the center of the weld, the thermo-mechanically affected zone was the portion that suffered heat and mechanical force over the tool head, the heat-affected zone was next that suffered heat and mechanical force over the tool head, the heat-affected zone was to the welded area that suffered heat generated during the FSP, and the unaffected zone next to the welded area that suffered heat generated during the FSP, and the unaffected was next to the heat-affected zone and the edge of the plates. The Vickers microhardness zone was next to the heat-affected zone and the edge of the plates. The Vickers microhard- tester (model: BHT 1000, manufacturer: Acme Engineers, city: Dhayari, state: Pune) was ness tester (model: BHT 1000, manufacturer: Acme Engineers, city: Dhayari, state: Pune) employed for this investigation. The preparation of the samples included them being was employed for this investigation. The preparation of the samples included them being finished and polished using a fine 800 grit emery sheet. The hardness measurement was finished and polished using a fine 800 grit emery sheet. The hardness measurement was taken in all the zones mentioned. Different test conditions were applied for a load of 400 g takenand maintained in all the zones for 20 mentioned. s; the indentation Different was te analyzedst conditions in all sampleswere applied and the for microhardness a load of 400 gvalues and maintained were recorded for 20 [19 s;]. the indentation was analyzed in all samples and the microhardness values were recorded [19]. 2.6. Characterization for Corrosion on Welded Samples 2.6. Characterization for Corrosion on Welded Samples The immersion corrosion test was conducted effectively with the specified ASTM standardsThe immersion G31-72; samples corrosion were test prepared was conduct with dimensionsed effectively of 20with× 15 the× specified6 mm from ASTM each standardsspecimen (seeG31-72; Figure samples4) at the were FSP prepared zone. The with surface dimensions of the specimens of 20 × 15 was × 6 polishedmm from using each specimen (see Figure 4) at the FSP zone. The surface of the specimens was polished using a 800 grit emery and cleaned by kerosene medium. The mass loss of all the specimens was measured directly by a digital weight balance; the samples were weighted before and after immersion.

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a 800 grit emery and cleaned by kerosene medium. The mass loss of all the specimens Materials 2021, 14, x FOR PEER REVIEW 8 of 17 was measured directly by a digital weight balance; the samples were weighted before and after immersion.

Figure 4. Corrosion tested samples of ( a) Expt. 1, 1, ( (b) Expt. 2, 2, ( (cc)) Expt. Expt. 3, 3, and and ( (dd)) Expt. Expt. 4. 4.

The corrosion characteristics of the samples were analyzed by way of an immersion test. The The corrosion corrosion medium medium was was prepared prepared at a 3.5% NaCl level and all the samplessamples were immersed individually in the corrosion solution.solution. The immersion time period maintained for the test was 48, 72,72, 96,96, andand 120120 hrs.hrs. AfterAfter ﬁnishingfinishing the immersionimmersion time period,period, the samples were taken out, allowed to dry, thenthen weightedweighted [[20].20]. The formula used for finding ﬁnding the corrosioncorrosion rate of the specimens was:

k × ∆W Corrosion rate( mm/yr) = , (1) Corrosion rate mm/yr , (1) ac × te × ρ where k = 8.76 × 104,te = time of exposure (hours), ac = cross sectional area of the specimen 4 (cmwhere2), ∆ kW = 8.76= reduction× 10 ,te in= timespecimen of exposure weight (hours), (g), ρ = amassc = cross density sectional of the area material of the (g/cm specimen3). (cm2), ∆W = reduction in specimen weight (g), ρ = mass density of the material (g/cm3). 3. Results and Discussion 3. Results and Discussion Different speeds (800, 900, 1000, and 1100 rpm) were used to produce the FSP sam- Different speeds (800, 900, 1000, and 1100 rpm) were used to produce the FSP samples ples for the tensile test. The specimens were tested, and the tensile strength of each speci- for the tensile test. The specimens were tested, and the tensile strength of each specimen is men is shown in Table 3. shown in Table3.

Table 3. TableFriction 3. stirFriction processing stir processing parameters parameters used. used.

Experi- Stirring (Tool Pin Traverse Speed of Compressive Stirring (Tool PinExperimental. Rotational) Traverse Speed of Tool Compressive Force on ToolTool Tilt Tilt Angle Angle in in mental. In- Rotational) Speed Tool Head (mm Force on Tool Speed (rpm)Index Head (mm per min) Tool (kN) DegreesDegrees dex (rpm) per min) (kN) 1 800 1 800 40 40 3 3 2 2 2 900 40 3 2 2 900 3 1000 40 40 3 3 2 2 3 1000 4 1100 40 40 3 3 2 2 4 1100 40 3 2 3.1. Tensile Strength of Friction Stir Processed Samples 3.1. TensileFrom theStrength tensile of test,Friction Figure Stir5 Processedshows the Samples connection between the stirring speed (tool rotational)From the and tensile the respective test, Figure tensile 5 shows strength the connection of the weld between produced the onstirring the sample. speed (tool The rotational)four samples and and the their respective tensile tensile strengths streng werethanalyzed; of the weld the produced maximum on tensile the sample. strength The of four284MPa samples was and reached their for tensile specimens strengths which were experienced analyzed; athe stirring maximum speed tensile of 1100 strength rpm. The of 284increase MPa inwas stirring reached speed for specimens increased thewhich strength experienced of the welding,a stirring helpingspeed of it 1100 to withstand rpm. The increasetensile loads, in stirring and vice speed versa. increased High speeds the strength induced of athe ﬁne welding, grain structure helping init theto withstand FSP zone. tensileTable3 loads,shows and the detailsvice versa. of the High process speeds parameters induced a employed fine grain instructure each experiment. in the FSP Fourzone. Tablesamples 3 shows were preparedthe details and of tested.the process parameters employed in each experiment. Four samples were prepared and tested.

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FigureFigure 5. 5.Average Average tensile tensile strength strength of ofof the thethe welded weldedwelded joints jointsjoints at atat various variousvarious stirring stirringstirring speeds. speeds.speeds.

FigureFigure 66 6presents presentspresents the the the stress–strain stress–strain stress–strain curvecurve curve ofof of the the the tensile tensile tensile test test test specimens. specimens. specimens. From From From the the fourthe four four tool toolspeeds,tool speeds, speeds, the the maximum the maximum maximum tool tool speedtool speed speed (1100 (1100 (1100 rpm) rp rp wasm)m) was produced was produced produced the bestthe the best tensile best tensile tensile strength strength strength in the inspecimens.in the the specimens. specimens. In the In fourIn the the tensilefour four tensile tests,tensile thetests, tests, maximum the the maximum maximum tensile tensile strength tensile strength strength was recorded was was recorded recorded as 284 MPa as as 284and284 MPa MPa the and minimum and the the minimum minimum tensile strengthtensile tensile strength wasstrength registered was was registered registered as 228 MPa. as as 228 228 MPa. MPa.

Exp Exp -1 -1 Exp - 2 300300 Exp - 2 Exp - 3 270 Exp - 3 270 Exp Exp - 4- 4 240240 210210 180180 150150 120120 Stress (MPa) Stress (MPa) 9090 6060 3030 0 0 0123456789101112131415161701234567891011121314151617 StrainStrain (e) (e)

Figure 6. Stress strainFigureFigure curves 6. 6. ofStress Stress the differentstrain strain curves curves specimens. of of the the different different specimens specimens 3.2. Hardness on Friction Stir Processed Samples 3.2.3.2. Hardness Hardness on on Friction Friction Stir Stir Processed Processed Samples Samples Table4 presents the microhardness values for the various zones of the FSP using Table 4 presents the microhardness values for the various zones of the FSP using differentTable tool 4 presents speeds. the Among microhardness the four speedsvalues for used, the using various atool zones speed of the of FSP 1100 using rpm different tool speeds. Among the four speeds used, using a tool speed of 1100 rpm pro- produceddifferent tool a high speeds. microhardness Among the value four of speed 148 Vickerss used, Hardnessusing a tool Number speed (VHN)of 1100 in rpm the pro- FSP duced a high microhardness value of 148 Vickers Hardness Number (VHN) in the FSP zone.duced In a thehigh thermo-mechanically microhardness value affected of 148 zone, Vickers it was Hardness 145 VHN; Number in the heat-affected(VHN) in the zone, FSP zone. In the thermo-mechanically affected zone, it was 145 VHN; in the heat-affected zone, itzone. was In 142 the VHN; thermo-mechanically and in the unaffected affected zone, zone it was, it was 84 VHN.145 VHN; in the heat-affected zone, it was 142 VHN; and in the unaffected zone, it was 84 VHN. it wasThe 142 inﬂuence VHN; and of in FSP the on unaffected the samples zone, in it terms was 84 of VHN. microhardness variation from the center of the weld to the extreme edges of the plate was investigated and presented in graphical form in Figure7. The hardness was measured in the FSP zone (that is, the center of the weld), the thermo-mechanically affected zone (that is, the portion that suffered heat and mechanical force over the tool head), the heat-affected zone (next to the welded area

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Table 4. Microhardness for the various zones of the FSP using different tool speeds.

Materials 2021, 14, 2782 Average Microhardness Values in Various Zones 9 of 15 Expt. Tool Pin Rotational Speed Heat-Affected Thermo-Mechanically Unaffected Zone FSP Zone Index (rpm) Zone Affected Zone 1 800 75 109 114 115 that suffered heat generated during the FSP), and the unaffected zone (next to the heat- 2 900 77 120 122 124 affected zone to edge of the plates). From the welding zone to the edge of the specimens, 3 1000 80 133 138 141 the length was divided into 10 equal distances on both sides (5 mm per division) and 4 1100 measurements were 84 carried out. 142 145 148

TableThe 4. Microhardness influence of for FSP the on various the samples zones of thein te FSPrms using of microhardness different tool speeds. variation from the center of the weld to the extreme edges of the plate was investigated and presented in Average Microhardness Values in Various Zones graphical form in Figure 7. The hardness was measured in the FSP zone (that is, the center Tool Pin Thermo- of theExpt. weld), the thermo-mechanicallyUnaffected affectedHeat-Affected zone (that is, the portion that suffered heat Rotational Mechanically FSP Zone Index Zone Zone and mechanical forceSpeed over (rpm) the tool head), the heat-affected zoneAffected (next Zone to the welded area that suffered1 heat generated 800 during 75 the FSP), and 109 the unaffected 114 zone (next to 115the heat- affected2 zone to edge 900 of the plates). 77From the welding 120 zone to the 122 edge of the specimens, 124 the length3 was divided 1000 into 10 equal 80 distances on 133 both sides (5 138 mm per division) 141 and 4 1100 84 142 145 148 measurements were carried out.

FigureFigure 7.7. VickersVickers microhardnessmicrohardness testtest graphgraph (distance(distance vs.vs. microhardness).microhardness).

TheThe maximummaximum hardness values values were were found found in in the the friction friction stir stir processing processing zone. zone. In the In thebase base (parent) (parent) material material zone, zone, the thevalue value of ha ofrdness hardness was was obtained obtained in the in the range range of of60 60to to80 80HV, HV, but but in inthe the FSP FSP zone zone the the range range was was from from 115 115 to to 155 155 HV [21]. [21]. During FSP, highhigh tooltool speedsspeeds brokebroke the the hard hard grains grains to to form form fine fine grains grai inns thein the structure structure at the at zonethe zone of stirring, of stirring, thus improvingthus improving the hardness. the hardness. An excellent An excellent hardness ha valuerdness of value 156 HV of 156 was HV found was in found the zirconia in the loadedzirconia on loaded the groove on the between groove thebetween sample the edges sample (the edges FSP stirring (the FSP zone) stirring with zone) regard with to the re- toolgard rotational to the tool speed rotational (1100 rpm).speed The(1100 zirconium rpm). The dioxide zirconium intensified dioxide the intensified hardness the value hard- in theness FSP value zone in [the22]. FSP zone [22]. 3.3. Corrosion Test Results of Friction Stir Processed Samples 3.3. Corrosion Test Results of Friction Stir Processed Samples Immersion corrosion testing was carried out at different time periods with 3.5% of Immersion corrosion testing was carried out at different time periods with 3.5% of NaCl corrosion medium, as illustrated in Table5. The tool rotational speed and corrosion NaCl corrosion medium, as illustrated in Table 5. The tool rotational speed and corrosion rate are shown in Table4. rate are shown in Table 4. The highest corrosion rate was obtained at the start of the test. Further increasing the time period caused the corrosion rate of the all samples to decrease consistently. The lowest corrosion rate of 0.0064 mm/yr was attained when a higher stirring speed (tool rotational) of 1100 rpm was influenced. Figure8 shows the relationship between the immersion and corrosion rate in relation to the10 stirring speed (tool rotational). Hence, it is understood that an increase in stirring speed reduces the corrosion rate significantly. Across the whole immersion time period, the sample for which a 1100 rpm tool rotational speed was used Materials 2021, 14, x FOR PEER REVIEW 11 of 17

Table 5. Summary of the corrosion test.

Tool Pin Rotational Corrosion Rate (mm/yr) Specimen No. Speed (rpm) 48 h 72 h 96 h 120 h Materials 2021, 14, 2782 10 of 15 1 800 0.0478 0.0324 0.0289 0.0263 2 900 0.0453 0.0312 0.0268 0.0247 3 1000 0.0387 0.0294 0.0186 0.00821 4 1100attained an excellent0.0324 corrosion resistance.0.0262 Microstructure0.0153 alteration increases0.0064 the corrosion resistance, suggesting that tool speed is the major factor in FSP [23–28]. The highest corrosion rate was obtained at the start of the test. Further increasing the time period caused the corrosion rate of the all samples to decrease consistently. The low- Table 5. Summary of the corrosion test. est corrosion rate of 0.0064 mm/yr was attained when a higher stirring speed (tool rotational) of 1100 rpm was influenced. Figure 8 shows the relationshipCorrosion between Rate the (mm/yr)immer- sionSpecimen and corrosion No. rateTool in Pinrelation Rotational to the Speed stirring (rpm) speed (tool rotational). Hence, it is un- 48 h 72 h 96 h 120 h derstood that an increase in stirring speed reduces the corrosion rate significantly. Across the whole1 immersion time period, 800the sample for which a 0.04781100 rpm tool 0.0324 rotational 0.0289 speed 0.0263 2 900 0.0453 0.0312 0.0268 0.0247 was used3 attained an excellent corrosion 1000 resistance. Microstructure 0.0387 0.0294alteration increases 0.0186 0.00821 the corrosion4 resistance, suggesting 1100 that tool speed is the major 0.0324 factor 0.0262 in FSP [23–28]. 0.0153 0.0064

FigureFigure 8. 8.CorrosionCorrosion test test graph, graph, imme immersionrsion vs. corrosion vs. corrosion rate. rate.

3.4.3.4. Results Results of ofOptical Optical Microscopic Microscopic Analys Analysisis on Friction on Friction Stir Processed Stir Processed Samples Samples OpticalOptical microscopic microscopic images images of ofthe the immers immersionion corrosion corrosion test test specimens specimens were were ob- obtained. tained.Figure Figure9 presents 9 presents the four the four SEM SEM images images of theof the after-corrosion after-corrosion test test specimens.specimens. These These images imagesshow thatshow the that use the of use different of different tool speedstool speeds causes causes various various defects defects on on the the corroded corroded specimens. specimens.Defects of Defects small holes of small due holes to variation due to variation in the melting in the melting of the grains of the aregrains shown are shown in Figure 9a–d . inThe Figure images 9a–d. in TheFigure images9a,b inshow Figure that 9a,b the show corrosion that the takes corrosion place takes evenly place and evenly that the and zirconium thatdioxide the zirconium particles dioxide are mixed particles well are and mixed appear well on and the appear surface on randomly.the surface randomly. In Figure 9c , it can In Figure 9c, it can be seen that the zirconium oxide particles are mixed uniformly and be seen that the zirconium oxide particles are mixed uniformly and only a small amount only a small amount of corrosion takes place. From Figure 9d, it can be seen that surface alterationof corrosion can be takes performed place. effectively From Figure and 9vedry, itlittle can corrosion be seen occurs that surface in the FSP alteration zone. can be Differentperformed defects effectively were identified and very in the little images corrosion, such as occurs pores, incracks, the FSP corrosion zone. channels, Different defects secondwere identiﬁedphase particles, in the small images, cavities, such and as de pores,bris. The cracks, corrosion corrosion varied based channels, on the second tool phase speed.particles, A high small tool cavities, speed offered and debris.low corrosion The corrosion defects. varied based on the tool speed. A high tool speed offered low corrosion defects.

3.5. Surface Morphological11 Investigation on Samples with 2D Proﬁlometry Images In Figure 10a, it can be seen that the lack of stirring action in the bottom area causes a higher corrosion rate compared to the other samples. Figure 10b shows that a reasonable corrosion rate was attained due to low rotational speed, due to lack of grain modiﬁcation in the FSP and it shown in a blue color. Figure 10c,d show that the corrosion takes place only in small amounts due to the high speed involved; the blue color is lightly shown in the image. Materials 2021, 14, 2782 11 of 15 Materials 2021, 14, x FOR PEER REVIEW 12 of 17

Materials 2021, 14, x FOR PEER REVIEW 13 of 17

Figure 9. OpticalFigure 9. microscopic Optical microscopic image image of corrosion of corrosion test test specimen: specimen: (a ()a Expt.) Expt. 1, (b 1,) Expt. (b) Expt.2, (c) Expt. 2, ( c3,) and Expt. (d) 3,Expt. and 4. (d) Expt. 4. 3.5. Surface Morphological Investigation on Samples with 2D Profilometry Images In Figure 10a, it can be seen that the lack of stirring action in the bottom area causes a higher corrosion rate compared to the other samples. Figure 10b shows that a reasonable corrosion rate was attained due to low rotational speed, due to lack of grain modification in the FSP and it shown in a blue color. Figure 10c,d show that the corrosion takes place only in small amounts due to the high speed involved; the blue color is lightly shown in the image.

(a) (b)

(c) (d) Figure 10. 2D laser profilometry of the corrosion test. (a) Expt. 1, (b) Expt. 2, (c) Expt. 3, and (d) Expt. 4. Figure 10. 2D laser proﬁlometry of the corrosion test. (a) Expt. 1, (b) Expt. 2, (c) Expt. 3, and (d) Expt. 4. 3.6. Surface Morphological Investigation on Samples with 3D Profilometry Images The SEM images (SEM; HITACHI, tested at AC Tech., Anna University, Chennai, India) were converted into 3D profilometry images of the corrosion test specimens; these are shown in Figure 10. The color scale bar indicates the blue, green, brown, and red colors for identifying the corrosion rate. In Figure 11a, the blue color shown in the bottom area shows that a large amount of corrosion took place. The small amount of blue color in Fig- ure 11b denotes that the area was moderately corroded. Figure 11c,d shows a little blue color, meaning a small amount of corrosion took place. From all the images, it can be seen that a high tool rotational speed decreased the corrosion rate and increased the corrosion resistance due to the sufficient alteration in the grain structure.

(a)

13 Materials 2021, 14, x FOR PEER REVIEW 13 of 17

(a) (b)

Materials 2021, 14, 2782 12 of 15

(c) (d) 3.6. Surface Morphological Investigation on Samples with 3D Profilometry Images Figure 10. 2D laser profilometry of the corrosion test. (a) Expt. 1, (b) Expt. 2, (c) Expt. 3, and (d) Expt. 4. The SEM images (SEM; HITACHI, tested at AC Tech., Anna University, Chennai, 3.6. SurfaceIndia) Morphological were converted Investigation into on 3D Samples profilometry with 3D Profilometry images Images of the corrosion test specimens; these Theare SEM shown images in Figure(SEM; HITACHI, 10. The colortested scaleat AC bar Tech., indicates Anna University, the blue, Chennai, green, brown, and red colors India) werefor identifying converted into the 3D corrosion profilometry rate. images In Figureof the corrosion 11a, the test blue specimens; color shown these in the bottom area are shown in Figure 10. The color scale bar indicates the blue, green, brown, and red colors for identifyingshows the that corrosion a large rate. amount In Figure of 11a, corrosion the bluetook color place.shown in The the bottom small amountarea of blue color in shows thatFigure a large 11b amount denotes of co thatrrosion the took area place. was moderatelyThe small amount corroded. of blue color Figure in Fig-11c,d shows a little blue ure 11bcolor, denotes meaning that the area a small was amountmoderately of corroded. corrosion Figure took 11c,d place. shows From a little allthe blue images, it can be seen color, meaningthat a high a small tool amount rotational of corrosion speed took decreased place. From the all corrosionthe images, rateit can and be seen increased the corrosion that a highresistance tool rotational due to speed the sufficientdecreased th alteratione corrosion in rate the and grain increased structure. the corrosion resistance due to the sufficient alteration in the grain structure.

Materials 2021, 14, x FOR PEER REVIEW 14 of 17

(a)

(b)

(c)

(d) Figure 11. 3D laser profilometry of the corrosion test: (a) Expt. 1, (b) Expt. 2, (c) Expt. 3, and (d) Expt. 4. Figure 11. 3D laser proﬁlometry of the corrosion test: (a) Expt. 1, (b) Expt. 2, (c) Expt. 3, and 4. Conclusions(d) Expt. 4. The novel approach of friction stir processing for AA8006 with zirconium dioxide (zirconia) was carried out using a straight cylindrical tool. The investigations of the tensile strength corrosion resistance and the Vickers microhardness were conducted and the values were measured. The outcomes of this research are as follows: • In the tensile test, all four specimens were tested, and all the specimens’ tensile strength increased with the increase in the stirring (tool rotational) speed. The maximum tensile strength obtained was 284 MPa with a stirring speed of 1100 rpm. This clearly confirms that an increased speed and high temperature modify the grains in the surface structure. • The hardness development in the FSP samples revealed an improved Vickers microhardness of 156 HV at the friction stir processing zone for a higher stirring speed of 1100 rpm. The investigation results show that there was an increase in the Vickers microhardness at the friction stir processing zone with an increase in the stirring speed. The microhardness of the base materials also improved a little.

14 Materials 2021, 14, 2782 13 of 15

4. Conclusions The novel approach of friction stir processing for AA8006 with zirconium dioxide (zirconia) was carried out using a straight cylindrical tool. The investigations of the tensile strength corrosion resistance and the Vickers microhardness were conducted and the values were measured. The outcomes of this research are as follows: • In the tensile test, all four specimens were tested, and all the specimens’ tensile strength increased with the increase in the stirring (tool rotational) speed. The maximum tensile strength obtained was 284 MPa with a stirring speed of 1100 rpm. This clearly confirms that an increased speed and high temperature modify the grains in the surface structure. • The hardness development in the FSP samples revealed an improved Vickers microhardness of 156 HV at the friction stir processing zone for a higher stirring speed of 1100 rpm. The investigation results show that there was an increase in the Vickers microhardness at the friction stir processing zone with an increase in the stirring speed. The microhardness of the base materials also improved a little. • The investigation of corrosion resistance in the friction stir processed samples revealed that the corrosion resistance could be altered by altering the stirring speed. The corrosion rate increased then gradually decreased when the length of immersion increased. The minimum corrosion rate achieved was 0.0064 mm/yr with a 1100 rpm stirring speed. • OM and SEM images of the 2D and 3D profilometry were taken to see whether the corrosion resistance of the all specimens was improved by the friction stir processing, It was found that using a lower stirring speed causes small holes in the friction stir-processed specimens. • Our findings are that the AA8006 material is friction stir weldable. The quality of the weld can be improved by friction stir processing. The rate of stirring decides the corrosion resistance, tensile strength, and microhardness in the welded zone. That is, the process can be controlled by altering the stirring speed to obtain the desired corrosion resistance, tensile strength, and microhardness. • This investigation utilized the well-known reinforcement agent zirconia for friction stir processing. Our investigation will be extended with some other reinforcements. This investigation considered AA8006 alloy plates with a fixed thickness for FSP. The thickness will be altered and standardized for commercial use.

Author Contributions: Conceptualization, T.S. and A.R.R.K.; data curation, V.M.; formal analysis, K.A., A.A. (Asif Afzal), and M.B.; funding acquisition, A.A. (Asif Afzal); investigation, M.B.; method- ology, A.A. (Abdul Aabid) and T.S.; project administration, K.A.; resources, B.S. and M.B.; software, M.B. and B.S.; supervision, A.A. (Asif Afzal), T.S., and M.B.; writing—original draft, B.S. and V.M.; writing—review and editing, A.R.R.K. and T.S. All authors have read and agreed to the published version of the manuscript. Funding: This research is supported by the Structures and Materials (S&M) Research Lab of Prince Sultan University. Furthermore, the authors acknowledge the support of Prince Sultan University for paying the article processing charges (APC) of this publication. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Raw data available from the corresponding authors upon request. Acknowledgments: This study is supported by Taif University Researchers Supporting Project number (TURSP-2020/49), Taif University, Taif, Saudi Arabia. The authors would like to thank Taif University for financial support. Conflicts of Interest: The authors declare no conflict of interest. Materials 2021, 14, 2782 14 of 15

Nomenclature

MPa Mega Pascal rpm revolution per minute Mm/min millimeter per minute FSP Friction Stir Processing FSW Friction Stir Welding SEM Scanning Electron Microscopy ON Optical Microscopy kN kilo-Newton te Time of Exposure ac cross sectional area ∆W reduction in specimen weight ρ mass density NaCl sodium chloride ASTM American Society for Testing and Materials G Grams UTM Universal Testing Machine CNC Computer Numerical Control ZrO2 zirconia (or) zirconium dioxide TIG Tungsten Inert Gas AMC aluminum metal matrix composite TiB2 titanium diboride BN boron nitride Al0.3CoCrCu0.3FeNi a kind of high-entropy alloy

References 1. Sharma, A.; Sharma, V.M.; Mewar, S.; Pal, S.K.; Paul, J. ‘Friction stir processing of Al6061-SiC-graphite hybrid surface composites. Mater. Manuf. Process. 2017, 1–9. [CrossRef] 2. Li, K.; Liu, X.; Zhao, Y. Research status and prospect of friction stir processing technology. Coatings 2019, 9, 129. [CrossRef] 3. Palanivel, R.; Dinaharan, I.; Laubscher, R.F.; Davim, J.P. Influence of boron nano particles on microstructure and wear behavior of AA6082/ TiB2 hybrid aluminium composites synthesized by friction stir processing. Mater. Des. 2016, 106, 195–204. [CrossRef] 4. Rana, H.; Badheka, V. Influence of Friction stir processing conditions on the manufacturing of Al Mg-Zn-Cu alloy/boron carbide surface composite. J. Mater. Process. Technol. 2018.[CrossRef] 5. Saravanan, R.; Rao, M.S.; Malyadri, T.; Sunkara, N. Profile optimization in tooltip for FSW process—A numerical investigation. In Recent Trends in Mechanical Engineering. Lecture Notes in Mechanical Engineering; Narasimham, G., Babu, A., Reddy, S., Dhanasekaran, R., Eds.; Springer: Singapore, 2020; pp. 373–385. [CrossRef] 6. Sivaraman, P.; Nithyanandhan, T.; Karthick, M.; Kirivasan, S.M.; Rajarajan, S.; Sundar, M.S. Analysis of tensile strength of AA 2014 and AA 7075 dissimilar metals using friction stir welding. Mater. Today Proc. 2020, 37, 187–192. [CrossRef] 7. Pandiyarajan, R.; Maran, P.; Marimuthu, S.; Arumugam, K. Mechanical and metallurgical characterization of friction stir welded AA6061-ZrO2-C hybrid MMCs. Mater. Today Proc. 2019, 19, 256–259. [CrossRef] 8. Sivaraman, P.; Prabhu, M.K.; Nithyanandhan, T.; Mohammed Razzaq, M.; Kousik, K.; Abraham, D.D. Development of aluminum based AA 2014 and AA 7075 dissimilar metals for aerospace applications. Mater. Today Proc. 2021, 37, 522–526. [CrossRef] 9. Ramamoorthi, R.; Yuvaraj, K.P.; Gokul, C.; Eashwar, S.J.; Arunkumar, N.; Dheen, S.A.T. An investigation of the impact of axial force on friction stir-welded AA5086/AA6063 on microstructure and mechanical properties butt joints. Mater. Today Proc. 2020. [CrossRef] 10. Mohamed, M.F.; Yaknesh, S.; Kumar, C.A.; Rajadurai, J.G.; Janarthanan, S.; Vignes, A.V. Optimization of friction stir welding parameters for enhancing welded joints strength using Taguchi based grey relational analysis. Mater. Today Proc. 2020, 39, 676–681. [CrossRef] 11. Lin, P.T.; Liu, H.C.; Hsieh, P.Y.; Wei, C.Y.; Tsai, C.W.; Sato, Y.S.; Chen, S.C.; Yen, H.W.; Lu, N.H.; Chen, C.H. Heterogeneous structure-induced strength-ductility synergy by partial recrystallization during friction stir welding of a high-entropy alloy. Mater. Des. 2021, 197, 109238. [CrossRef] 12. Sanusi, K.O.; Akinlabi, E.T. Friction-stir processing of a composite aluminum alloy (AA 1050) reinforced with Titanium carbide powder. Mater. Techol. 2017, 3, 427–435. [CrossRef] 13. Selvakumar, S.; Dinaharan, I.; Palanivel, R.; Babu, B.G. Development of stainless steel particulate reinforced AA6082 aluminum matrix composites with enhanced ductility using friction stir processing. Mater. Sci. Eng. A 2017, 685, 317–326. [CrossRef] 14. Sivanesh Prabhu, M.; Elaya Perumal, A.; Arulvel, S.; Franklin, I.R. Friction and wear measurements of friction stir processed aluminium alloy 6082/CaCO3 composite. Measurement 2019, 10–20. [CrossRef] Materials 2021, 14, 2782 15 of 15

15. Thangarasu, A.; Murugan, N.; Dinaharan, I.; Vijay, S.J. Synthesis and characterization of titanium carbide particulate reinforced AA6082 aluminium alloy composites via friction stir processing. Arch. Civil Mech. Eng. 2014.[CrossRef] 16. Suvarna, R.L.; Kumar, A. Influence of Al2O3 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing. Def. Technol. 2014, 10, 375–383. [CrossRef] 17. Sudhakar, I.; Reddy, G.M.; Rao, K.S. Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing—An experimental study and analytical approach. Def. Technol. 2016, 12, 25–31. [CrossRef] 18. Du, Z.; Tan, M.J.; Guo, J.F.; Bi, G.; Wei, J. Fabrication of a new Al-Al2O3-CNTs composite using friction stir processing (FSP). Mater. Sci. Eng. A 2016, 667, 125–131. [CrossRef] 19. Dinaharan, I.; Akinlabi, E.T.; Hattingh, D.G. Microstructural characterization and sliding wear behavior of Cu/TiC copper matrix composites developed using friction stir processing. Metallogr. Microstruct. Anal. 2018, 7, 464–475. [CrossRef] 20. Liu, D.; Xin, R.; Zhao, L.; Hu, Y.; Zhang, J. Evaluation of corrosion and wear resistance of friction stir welded ZK60 alloy. Sci. Technol. Weld. Joining 2017, 22, 601–609. [CrossRef] 21. Abreu, C.M.; Acuña, R.; Cabeza, M.; Cristóbal, M.J.; Merino, P.; Verdera, D. Microstructure and mechanical properties of Al/SiC composite surface layer produced by friction stir processing. Ciencia Tecnol. Mater. 2017, 29, e82–e86. [CrossRef] 22. Rana, H.G.; Badheka, V.J.; Kumar, A. Fabrication of Al7075 / B4C surface composite by novel Friction Stir Processing (FSP) and investigation on wear properties. Proc. Technol. 2016, 23, 519–528. [CrossRef] 23. Chaluvaraju, B.V.; Afzal, A.; Vinnik, D.A.; Kaladgi, A.R.; Alamri, S.; Tirth, V. Mechanical and corrosion studies of friction stir welded nano Al2O3 reinforced Al-Mg matrix composites: RSM-ANN modelling approach. Symmetry 2021, 13, 537. [CrossRef] 24. Nagaraja, S.; Nagegowda, K.U.; Kumar, V.A.; Alamri, S.; Afzal, A.; Thakur, D.; Kaladgi, A.R.; Panchal, S.; Saleel, C.A. Influence of the fly ash material inoculants on the tensile and impact characteristics of the aluminum AA 5083/7.5SiC composites. Materials 2021, 14, 2452. [CrossRef] 25. Sharath, B.N.; Venkatesh, C.V.; Afzal, A.; Ahmed, M.; Baig, A.; Kumar, A.P. Study on effect of ceramics on dry sliding wear behaviour of Al-Cu-Mg based metal matrix composite at different temperature. Mater. Today Proc. 2021. [CrossRef] 26. Sharath, B.N.; Jeevan, T.P.; Baig, M.A.; Ashrith, H.S.; Afzal, A.; Reddy, A.R. Machinability studies on boron carbide and graphite reinforced aluminium hybrid composites. Mater. Today Proc. 2021.[CrossRef] 27. Guggari, G.S.; Shivakumar, S.; Nikhil, R.; Manjunath, G.A.; Afzal, A.; Saleel, C.A. Experimental investigation of mechanical properties of Acrylonitrile Butadiene Styrene ( ABS ) based polymer for Submersible pumps Experimental investigation of mechanical properties of Acrylonitrile Butadiene Styrene ( ABS ) based polymer for Submersible. IOP Conf. Ser. Mater. Sci. Eng. 2021, 1065, 12035. [CrossRef] 28. Kaladgi, A.R.; Rehman, K.F.; Afzal, A.; Baig, M.A.; Soudagar, M.E.; Bhattacharyya, S. Fabrication characteristics and mechanical behaviour of aluminium alloy reinforced with Al2O3 and coconut shell particles synthesized by stir casting Fabrication characteristics and mechanical behaviour of aluminium alloy reinforced with Al2O3 and c. IOP Conf. Ser. Mater. Sci. Eng. 2021, 1057. [CrossRef]