EXPERIMENTAL EVALUTION OF FRICTION STIR WELDED JOINTS OF

EXPERIMENTAL EVALUTION OF FRICTION STIR WELDED JOINTS OF DISSIMILAR

ALUMINIUM PLATES

ByB.Sindhu13011D3317M.Tech-AMS

UNDER THE GUIDANCE OF Dr. G.KRISHNA MOHANA RAO

PROFESSOR MECHANICAL DEPARTMENT

CONTENTS:

AbstractIntroductionObjectiveInput parameters(process parameters)Experimental setupReferences

ABSTRACT:Aluminium alloys are being used increasingly for aerospace, automotive,

defense and structural applications to derive the benefits of considerable

savings in weight with high strength.

Welding of dissimilar aluminium alloys is often required for these applications.

Fusion welding of aluminium alloys leads to several problems such as porosity

and cracking.

Friction Stir Welding(FSW) is the latest technique amongst the Solid State

Welding(SSW)processes being used for joining aluminium alloys.

Furthermore, research is underway for establishing the suitability of FSW

technique for joining dissimilar metals , being a solid state welding process in

which melting and solidification do not take place.

INTRODUCTION:Friction stir welding is a new joining method derived from conventional

friction welding.

Friction Stir Welding has been used to weld aluminium alloys including

some of which are classified as unweldable by fusion welding techniques.

Friction stir welding is a suitable method for joining dissimilar alloys as

improved weld strength is expected in these weldments.

It is essential that while attempting to improve the tool wear rate and life ,

tool coating is considered(PVD coating).

Contd..,• Coated tools have compound material structure, consisting of the substrate

covered with a hard, anti friction, chemically inert and thermal isolating

layer, approximately one to few micron thick.

• As such coated tools compared with uncoated ones, offer better protection

against mechanical and thermal loads.

• Diminish friction and interactions between tool and chip and improve wear

resistance in a wide cutting temperature range.

ADVANTAGES OF TiAlN COATING:Low amount of heat generatedHigh hardnessSuperior wear resistanceGood oxidation resistanceExcellent corrosion resistanceExtensive plastic flow of materialVery fine grain size in the stirred region Random disorientation of grain boundaries in stirred region Controlled flow of materialHigh joint efficiencies (competitive with riveting and bonding).

OBJECTIVE:

To study the effect of TiAlN coated HSS tool on the weld strength during

Friction Stir Welding of AA6063 and AA6082 aluminium alloys.

To establish the friction stir welding process on 6mm thickness of AA6082,

AA6063 dissimilar aluminum alloy plates jointed using the parameters of

1. rotational speed(rpm)

2. welding speed(mm/min)

To study the mechanical properties of dissimilar friction stir weld joints

between AA6063 and AA6082 using with and without coated tool.

TOOL SPECIFICATIONS:Tool - HSS(High Speed Steel)

Tool pin profile - Hexagonal

Tool dimension: tool length = 80mm,

tool diameter = 18mm,

tool pin diameter =6mm ,

tool pin length = 5.8mm .

Coating material = TiAlN (PVD-Physical Vapor Deposition)

Coating thickness = 4 microns

Coating done in vacuum at low pressures in the temperature

range of 450-900˚ C .

MATERIALS AND ITS COMPOSITION:MATERIALS:

AA6082-AA6063 alluminium alloys

CHEMICAL COMPOSITION OF AA6082:

Weight %

Al Si Fe Cu Mn Cr Mg Zn Ti Others each

Others total

Alloy6082

Bal 0.7-1.3

0.50max

0.10 max

0.40-1.00

0.25max

0.06 -1.20

0.20 max

0.10max

0.05max

0.1 5max

Contd..,

Weight % Al Cu Fe Mg Mn Si Ti Zi Cr

AA6063 bal 0.1 0.35 0.45-0.9

0.1 0.2-0.6

0.1 0.1 0.1

• CHEMICAL COMPOSITION OF AA6063:

Schematic diagram of dissimilar aluminium base materials

Process parameters and their levels:

Process parameter

Level 1 Level 2 Level 3

Tool rotation speed(rpm)

1000 1400 2000

Welding speed(mm/min)

20 28 40

EXPERIMENTAL SETUP:The base materials used in this investigation is 6mm thick AA6063

and AA6082 aluminium alloy plates.HSS tool is used for conducting FSW experiments. Experiments are

conducted using HSS tool with coating (TiAlN) and without coating.Coating processes is done by using PVD (Physical Vapor Deposition)

processes. The hardness values and tensile strength of the specimens were

calculated .

EXPERIMENTAL SETUP:

Vertical milling machine used in Plates are welded because of the experimentation. the frictional heat generated.

RESULTS AND DISCUSSIONS:Strength analysis and hardness tests are carried out.• Strength analysis is carried out to know the ultimate tensile strength (UTS),

elongation percentage and yield stress of welded joints. • Hardness test carried out in the weld zone gives the data related to the

hardness of welded joints.

SPECIFICTAIONS OF TENSILE SPECIMEN:

ASTM E8 standard tensile specimen

tensile specimen after tensile testing

Sample No. Ultimate tensile strength (N/mm2)

1 69.361

2 49.66

3 48.25

4 75.06

5 92

6 87.07

7 83.78

8 78.23

9 52.31

TENSILE TEST RESULTS:

HARDNESS OBSERVATIONS:

Contd..,

From the above result we can conclude that ,the sample welded using the coated tool is more harder than the one which is welded using non-coated tool.

Combination of coated and non coated tool’s Tensile test results:

• Coated tool: ultimate load =16.64kN, deflection of 4.2mm.• Uncoated tool: ultimate load=10.28kN, deflection of 8.1mm.• From the above result we can

conclude that ,the sample welded using the coated tool have more ultimate load than the one which is welded using non-coated tool.

0 1 2 3 4 5 60

2

4

6

8

10

12

14

16

18 Load on Y-Axis Vs Disp (mm)

without coatingwith coating

Displacement (mm)

Load

(kN

)

Conclusions:The butt joint configuration of dissimilar aluminium joints was successfully

welded using TiAlN coated tool using FSW.The FSW tool with coating (TiAlN) and without coating is used for comparison

of weld strength and hardness values. To produce better tool life and tool wear rate tool coating is considered.

The tool rotational speed analysis has been carried out on AA6063 and AA6082 alloy plates. From the analysis of results, a traverse speed of 28 mm/min, tool rotational speed of 1400 rpm produced maximum weld strength.

And traverse speed of 28 mm/min, tool rotational speed of 2000 rpm produce maximum hardness values.

The weld properties of the dissimilar aluminium alloy joints are influenced by the coating and without coating tool. Coated tool produced better weld strength.

Sticking of the base metal on the tool pin. After each weld material from the base metal was sticking on the tool surface which affects the succeeding specimens. Further analysis should be done on tool and material matrix velocity to prevent this sticking phenomenon.

REFERENCESR.F. Tylecote , The Solid Phase Welding of Metals, Edward Arnold

(Publishers) Ltd, London, UK, 1968.B. Bhushan , Introduction to Tribology , John Wiley & Sons, Inc., Ohio,

USA, (2002). J. Williams, Engineering Tribology , Cambridge University Press,

Cambridge, USA, (2005). J. Halling , Princilples of Tribology , The Macmillan Press Ltd, London,

UK, (1983).R.S. Mishra and Z.Y. Ma, Friction Stir Welding Processing, Materials

Science and Engineering, R 50,(2005), PP. 1-78.

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