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A Brief Review of Friction Stir Welding Between Dissimilar Aluminium

Alloy and Pure Copper

1Pratikrajsinh Gohil,2Unnati Joshi,3Tejas Vyas

123Department of Mechanical Engineering,1PG Student,2Associate Professor,

3Assistant Professor

123 Parul Institute of Technology, Vadodara, Gujarat

[email protected]

Abstract

Friction Stir Welding (FSW) is a solid state welding process capable of welding dissimilar materials such as aluminum and copper having wide range of industrial applications. The welding process is

widely used because it produces quality welds with good joint strength exhibiting none or a few amount

of intermetallic compounds. Copper and aluminum dissimilar joining is important for taking advantage of properties of both the materials such as electrical conductivity, thermal conductivity and corrosion

resistance. In this paper we review the research work done in past between aluminum and copper

joining by friction stir welding with a focus on resulting weld mechanical properties and microstructure

by optimization of the process parameters and FSW tool pin positioning such as tool pin offset, tool tilt angle and tool design features with a view for dissimilar aluminum and copper joining. It also includes

the future research in this field of welding.

Keywords – Friction stir welding, aluminium, copper, dissimilar materials, optimization, mechanical

properties and microstructure.

I. INTRODUCTION

Producing a good quality weld between dissimilar materials such as copper and aluminium with a good

joint strength is a challenging and complicated task for researchers and engineers. In the current

competitive world of industrial development that need requirement of different and various properties in a

single component or a part that can only be fulfilled by the effective joining of two dissimilar materials.

Aluminium and copper possess good electrical conductivity, thermal conductivity and corrosion

resistance that make them applicable for producing parts or components that require good electrical and

thermal conductivity for its application. Friction stir welding is an effective solid state welding technique

that can efficiently produce a good quality weld between the dissimilar materials. The capability of

friction stir welding to join separate dissimilar materials without melting is a unique feature of friction stir

welding. Friction Stir Welding (FSW) is a solid–state joining technique invented by The Welding

Institute (TWI) in 1991 for welding of ferrous and non–ferrous metals. Recently the technique is also

used for welding of polymer materials as well as welding between a metallic material and polymer. FSW

has developed as a huge improvement in metal joining in recent decade and is capable of welding

materials such as aluminium alloys, copper alloys, titanium alloys, mild steel, stainless steel and

magnesium alloys.

Journal of Information and Computational Science

Volume 10 Issue 4 - 2020

ISSN: 1548-7741

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mailto:[email protected]

A) Principle of operation.

Friction stir welding employs a non consumable rotating welding tool that has a probe or a pin that

extends below a shoulder which is fully penetrated between the two adjacent mating surfaces of the

workpieces as shown in fig 1. As the tool is traversed along the joint line, it mechanically pressurizes and

forges the two pieces of metal. Heat is formed by the friction between the revolving tool and the

workpiece material, which develops a soft region near the FSW tool of metal, and forges the hot and

softened metal by the mechanical pressure. Stirring of the tool along the joint line in traverse direction

uniformly joins the two edges of the adjacent workpieces as a result of welding. Advancing sides and the

retreating sides are the two different sides of the two work samples.

Fig. 1 Principle of operation of FSW [1]

B) FSW Tool

The FSW tool plays a significant and vital role for effective joining and leading the material flow

along the joint line along the traverse direction. The FSW tool consists of three parts: a shank,

shoulder and the pin or a probe with shoulder and pin the main parts of the tool as the shoulder

makes full contact on the upper surface of the interface at the joint line with the pin which is fully

inserted into the workpiece. Different tool design and geometry exhibit different mechanical

properties and microstructure of the welded joint due to the variation in tool geometry and is

majorly responsible for quality of weld. Thus the FSW tool is better known as the heart of the

joining process.

The following are the different types of tools used in friction stir welding are:

1) Straight Cylindrical

2) Threaded Cylindrical

3) Tapered Cylindrical

4) Square

5) Triangle

Journal of Information and Computational Science

Volume 10 Issue 4 - 2020

ISSN: 1548-7741

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Fig.2 Basic FSW tool pin profiles [2] Fig.3. Schematic View of FSW Tool [3]

C) Friction stir welding process parameters :

Tool rotation and traverse speeds

There are two types of tool speeds in friction-stir welding process as the velocity at which the tool

rotates and velocity at which it moves or traverses down the interface. The above two parameters

have significant importance and must be chosen with care to make sure a successful and efficient

welding cycle. The relationship between the rotation speed, the welding speed and the heat input

during welding is complex but it can be said that increasing the rotation speed or decreasing the

traverse speed will result in a hot weld.

Tool tilt and plunge depth

The plunge depth is defined as the depth of the lowest point of the shoulder below the

surface of the welded plate and has been seen as a basic parameter for guaranteeing weld

quality. As we plunge the shoulder below the plate surface it increase the pressure

beneath the tool and helps ensure adequate forging of the material. As we tilt the tool by

2–4 degrees, such that the rear of the tool is lower than the front, has been found to assist

the weld bonding for good joint strength for dissimilar FSW of aluminium and copper

Tool pin offset

The tool pin offset is defined as the offset of the tool pin from the weld centerline towards a

particular base material. Zero tool pin offset means the welding tool axis is exactly at the

centerline of the interface between the two welded work samples. It is recommended that the

conventional method of FSW welding where pin is inserted at the weld centre line produced poor

and imperfect joints in dissimilar FSW [4, 5,6,7,8]

Journal of Information and Computational Science

Volume 10 Issue 4 - 2020

ISSN: 1548-7741

www.joics.org193

II. PAST STUDIES ON FRICTION STIR WELDING BETWEEN ALUMINIUM

ALLOYS AND COPPER

A. Optimization of the process parameters

In a developing field of dissimilar material welding optimization will be considered as a

significant technique to improve its application fields. Optimization deals with obtaining

process parameters accurately to certain value from a series of values having long range. So

accurate value achievement will reduce cost and also develop and improve its output

parameters

Sachindra Shankar et al.[9] conducted friction stir welding of aluminium alloy 1050 to pure

copper joint by varying two values of rotational speed such as 1400 rpm and 2000 rpm and

two values of traverse speed such as 40 and 63 mm/min with 2mm tool pin offset and keeping

all the other parameters such as tool design and geometry and tool tilt angle as constant.

Mechanical tests such as tensile test, microhardness tests and FESEM tests were implemented

to inspect the joint strength and microstructural property respectively. It was concluded that

the optimum set of parameters include the tool rotational speed of 1400 rpm and tool traverse

speed of 63 mm/min fabricated defect free welded joints. Highest joint strength acquired was

approximately 91% of Al parent metal in weld nugget by taking the 2 mm offset of the tool

on the Al side and fine-grained microstructure was observed in the weld nugget

Nitish kumar et al. [10] evaluated tensile strength in friction stir welded aluminum alloy

6101-T6 and commercially pure copper joints by conducting an experimental study to

optimize the critical process parameters such as tool geometry, shoulder diameter to pin

diameter ratio, welding speed, rotational speed and pin offset on the tensile behavior of

friction stir welded between aluminum alloy 6101-T6 and commercially used pure copper

using Taguchi’s L 16 design of experiment. Thorough mixing of dissimilar materials in

nugget zone was observed corresponding to best experimental