A Review on Optimization of the Process Parameters in Friction Stir Welding of Aluminium Alloys (AA6082 and AA6105) by Taguchi Technique

This study is describing a simple and systematic methodology for optimizing the Process parameters of friction stir welding (FSW) of (AA6105 and AA6082) aluminium alloy using Taguchi technique. The main focus of this review paper is to discuss FSW principle, process parameter and mechanical properties. The current study focuses on the friction stir welding of wrought aluminium alloys 6082 and aluminium alloy 6105 that are commonly used in the structural and automotive industries. Apart from this paper FSW process has been done on various aluminium alloys but dissimilar friction stir welding of these two materials are not reported in their research. A systematic study has been performed on the joint properties on the dissimilar welding of the selected materials and their relationships between various parameters.


Introduction
Alu miniu m is a soft, light-weight metal recognized in dull silvery white look. Alu minu m has become especially a supreme metal within the nineteenth century due to its lightweight weight and corrosive resistant properties. . It is 3 times lighter than steel and still; it o ffers h igh strength in its alloy type. It has lower in density (2.7 g m. /cm 3 ), low in melting temperature (Tm=660°C) and face centered cubic crystal (FCC) structure that makes Alu minu m element to be created and fabricated a lot of simple and with less value. Pure alu minum is soft and has a low strength of 40-50 MPa in tempered condition. It is reinforced by undergoing many processes like alloying and heat treatment. Alu minu m alloys offer a good vary of capability and applicability due to its many advantages that makes the material in demand in fabrication industries, automobile industries, aeronautical industries and other structural applications of transport and buildings. If we are talking about 6xxx series 6xxx series represent underneath the group of molded component metal alloys with Silicon and Magnesium is the major alloying elements. These alloys represent a majo r portion of architectural and structural applicat ions attributable to its wonderful formability when high strength to weight ratio is crucial. Alu miniu m alloy 6082 is one of the foremost widely used Al alloys due to its formability, good strength and high corrosive resistance. Aluminiu m alloy 6105 is heat treatable forged Al alloy with the composition of Si, Mg, and copper as major alloying parts .   [11]. If we are talking about the standard fusion weld ing process, where the material is to be joined is liquefied and resoldified, FSW wo rks on the principle of co mp lete material defo rmation. Ho wever, the material is joined with in the solid state by the heat generated within the interface by the friction and by the flow of materials as the result of intense stirring action. As the compressive force increase by the tool the diffusion process start and this diffusion is responsible for the join ing of the metal. And the metal join by diffusion is defect free.

Advantages of Friction Stir Welding
Some of the unique advantages of the FSW are discussed in this section 1. Green Technology FSW is called as the green energy weld ing due to its environmental friendliness and versatility. Un like fusion weld ing process, FSW is an autogenous process. FSW does not use flux, shielding gases, and filler material.

2.
Improved Weldability FSW has been successfully employed in joining materials that are considered to be unweldable by conventional weld ing techniques. Few cast metals that are d ifficu lt to weld due to the format ion of brittle phases and cracking are also successfully joined by FSW.

3.
Safety FSW is considered as a safe process as it devoid of toxic fumes or the spatter of molten material. Contradicting to the conventional weld ing, there are no ultrav iolet or electro magnetic radiat ion hazards as the absence of the arc removes these hazards from the process.

4.
Reduced distortion As the friction stir weld ing process is conducted below the re crystallization temperature, it reduces the longitudinal and transverse distortion. Thus the absence of fusion removes much of the thermal contraction associated with solidification and cooling, leading to significant reductions in distortion. Reducing distortion, in turn, reduces time and money in the post-weld treat ment process of the material in the manufacturing industry.

5.
Improved appearance FSW gives a good weld appearance after weld ing. It does not require high jo int preparation for weld ing. It does not involve expensive machining after weld ing. The root side of the weld and the weld interface are v irtually invisible after painting.

6.
Improved mechanical properties The results of the tests like tensile tests, hardness test, fatigue and bend tests show better improvement in the mechanical properties when compared to other fusion processes like TIG and MIG.

7.
Easily automated FSW is a robust process and can be easily auto mated on simp le milling machines, thus lowering setup costs. High skilled labor is not required like conventional fusion weld ing. It can be operated in all position (vertical, horizontal, inclined).

Lakshminarayanan and B alasubramani an (2008)
explore the different process parameter on tensile strength and yield strength. They applied the Taguchi approach to find the optimu m condition at wh ich they both term having high value. The material that is chosen for fsw is RDE-40 alu minu m alloy. It also is noted that rotation speed, weld ing speed are the main parameter for calcu lating the tensile strength and yield strength. Priya et al (2009) studied the effect of post weld heat treat ment on the microstructure and mechanical properties of dissimilar friction stir elements of AA6061 and AA2219. During their study, it is found that hardness has the main effect on the weld zone and when we co mpare HAZ with direct post weld zone there is no effective improvement. But at 555 °c and aging temp 165 °c , there is some improvement in hardness off weld zone and she also studied that postweld aging has not any influence on hardness. G.Padmanaban, V.Bal asubramani an (2009) has done an experiment using friction stir welding on AZ 31B magnesiu m alloys. During this, they inves tigate the selection of FSW tool pin profile shoulder diameter and material. They found that the joint fabricated by high carbon steel tool with threaded profile and shoulder diameter of 18mm having high tensile properties and absence of defects in nugget region. has studied FSW, its process parameters, the principle of operation, advantage & disadvantages. During its study, they found that principle of FSW and essential factors that affect the quality of weld and the critical analysis realize the possible research works on other than aluminu m alloys such as mild steel (work piece) and cubic boron nitride (tool), with same process parameters. Pavan Kumar et al., (2016) studied the comparison of microstructure and mechanical properties of friction stir weld ing of alu minu m 6082 with different tool profile .rotational speed is1400 rp m weld ing speed is constant 90mm/ min .electron microscope is used to test the fracture surface. During analysis, they found that mechanical and metallurgical properties are affected by tool profile. Dhananjaya Av vi a, DK Deried (2017) performed FSW on AA6082 During the study the effect of process parameter on mechanical and micro structured properties of similar AA6082 jo int is studied. After study they found that the value of micro hardness is weld zone at 48mm / min are higher than other welding speed, increase welding speed leads to the increase in tensile strength. S.Verma et al (2017) studied the temperature distribution deriving FSW o f A lu minum 6082 alloy, the temp distribution is captured using thermocouple during FSW of 6082 for varying this angle the max temp is attained on when tilt angle in 2° rotation speed 600 rpm well 30sec. M.V.R.Durga Prasad, Kiran Kumar Namal (2018) performed frict ion stir welding on AA5083 and AA6063 to study the process parameter optimizat ion by ANOVA. The process parameters considered are rotation speed, weld ing speeds, and tilt angle. During their optimization, they find that welding speed has the major factor. The maximu m value of hardness at tool rotation speed 1200rp m, weld ing speed of 80mm/min and tilt angle of 0 °. Malkeshwar, Vinodkumar et al (2018) performed a test using FSW on 5mm p lates of aluminiu m AA6061, AA6082 and AA19500 to determine the micro hardness & micro structural of jo int. Different values of welding speed, rotation speed & shoulder diameter were taken. During studied they find that tensile strength of similar metal is more than dissimilar metal. K. N. Wakchaure et al (2018) shows the experimental and numerical investigation of frict ion stir welding on AA6082-T6. The object ive of this research is to mu lti-response optimization of FSW for an optimal parametric co mb ination to yield favorable tensile strength and impact. During study they find that tool rotation speed and welding speed have maximu m influence on mechanical properties rather than tool tilt angle.

III.
CONCLUSIONS There are many kinds of literature available on the study of these two materials. The dissimilar frict ion stir weld ing of these two materials are not reported in their research work. In this dissimilar friction stir welding of AA6082 and AA6105 is reviewed. The effect of the process parameters on the mechanical properties of AA6082 and AA6105 is yet to be reported. The present work aims at studying the effect of process parameters on the mechanical properties of the FS welding of alu min iu m alloys AA6082 and AA6105.after reviewed the past literature it is also found that rotational speed, weld ing speed and tilt angle are the majo r process parameters. With changing the welding speed and rotational speed there is change in the hardness and tensile strength.