INVESTIGATION OF MECHANICAL, STRUCTURAL AND TRIBOLOGICAL PROPERTIES OF ALUMINIUM

METAL MATRIX COMPOSITE (AMMC’S) FABRICATED BY FRICTION STIR PROCESSING

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CHAPTER-1SYNOPSIS:

Aluminium has any attractive properties compared to steel used in

aerospace, automobile, marine and other industries. Due to their high strength

and light weight, appearance, frabricability and corrosion resistance. The

requirement of excellent properties such as high specific strength, superior wear

resistance, and low thermal expansion has empathized. The use of aluminium

metal matrix composite, friction stir processing is a solid state technique based

on principle of friction stir welding is used for material processing in order to

modify microstructure and mechanical properties. The non-consumable tool

rotates and simultaneous. The tool has downward force that pushes it again the

joint and linear that permit it to complete the process.

In the presence, AA5083-H111/Nano Al 2O3 AMC (aluminium

matrix composite) will be produced by friction stir process technique, in order

to investigate the mechanical, structural and tribological properties.

The optimised parameters will be consider based on literature AA5083-H111

that is rotational speed of 1000RPM , welding / transvers speed 40mm/min

straight square tool pin profile. After processing the test specimen will be

prepared to ASTM to evaluate the micro hardness and tensile properties also

microstructure the processed AMC‘s will be studied.

KEYWORDS: Aluminium metal matrix composites, hardness, tensile strength,

friction stir processing weld structure.

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CHAPTER-2INTRODUCTION

Friction stir processing (FSP)

It is a method of changing the properties of a metal through intense,

localized plastic deformation. This deformation is produced by forcibly inserting

a non-consumable tool into the work piece, and revolving the tool in a stirring

motion as it is pushed laterally through the work piece. The precursor of this

technique, friction stir welding , is used to join multiple pieces of metal without

creating the heat affected zone typical of fusion welding.

When ideally implemented, this process mixes the material without

changing the phase (by melting or otherwise) and creates a microstructure with

fine, equated grains . This homogeneous grain structure, separated by high-angle

boundaries, allows some aluminium alloys to take on superplastic properties.

Friction stir processing also enhances the tensile strength and fatigue strength of

the metal. In tests with actively cooled magnesium-alloy work pieces, the micro

hardness was almost tripled in the area of the friction stir process.

Process

In friction stir processing (FSP), a rotating tool is used with a pin and a shoulder

to a single piece of material to make specific property enhancement, such as

improving the material’s toughness or flexibility, in a specific area in the micro-

structure of the material via fine grain of a second material with properties that

improve the first. Friction between the tool and work pieces results in localized

heating that softens and plasticizes the work piece. A volume of processed

material is produced by movement of materials from the front of the pin to the

back of the pin. During this process, the material undergoes intense plastic

deformation and this results in significant grain refinement. FSP changes

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physical properties without changing physical state which helps engineers

create things such as “high-strain-rate super plasticity”. The grain refinement

occurs on the base material improving properties of the first material, while

mixing with the second material. This causes for the base material’s properties.

This allows for a variety of materials to be altered to be changed for things that

may require other difficult to acquire conditions. The processes branches off of

friction stir welding (FSW) which uses the same process to weld two pieces of

different materials together without heating, melting, or having to change the

materials’ physical state. Fig 2.1 shows process of friction stir process

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FIG 2.1 SHOWS THE PROCESS BEHIND FRICTION STIR PROCESS

CHAPTER-3OBJECTIVES:

I. To summarize the composite of friction stir processing technology.

II. Prepare design matrix to trial run of friction stir processing using design

of experiments which varies welding parameters.

III. Preparation of Nano powders using anyone available synthesis technique.

IV. Fabrication of weldment with reinforced or doping. Nanoparticle into

matrix material using optimal speed, transvers speed, tool pin profile or

characterisation of friction stir processing joints.

V. Characterisation of mechanical, structural and tribological properties of

friction stir processing joints.

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CHAPTER-4APPLICATION OF AA5083-H111

Shipbuilding

Vehicle bodies

Pressure vessels

Marine applications

Drilling rings

Transportation equipment’s

TV and communication towers

SHIPBUILDING

The application of aluminium alloys is increasing in all the industries

due to its combination of properties as

Low weight

Good mechanical resistance and

Good corrosion resistance

One of the industries where the application of aluminium is becoming

more important is shipbuilding which is one of main responsible for the

transport of people and goods in the world. The need of fast and less expensive

ships, demands for the advantages of Friction Stir Welding (FSW). Typically,

shipbuilding applies wrought aluminium alloys of series 5XXX and 6XXX.

The transfer of the FSW into industrial applications, such as shipbuilding,

demands for a detailed investigation about the influence of corrosion in the

performance of both parent materials and welded joints. The main mechanisms

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of corrosion that have been evaluated in AA5XXX are the intergranular

corrosion and the exfoliation. (1)

Fig. High speed aluminium ferry containing numerous friction stir welded components. (Hydro Aluminium). 

VEHICLE BODIES Today, the new revolution in car design is the use of new materials

in the vehicle structure.

As fuel economy restrictions become tighter, manufacturers must find new ways to meet them.

This has led them away from using so much steel in the vehicles, and more and more are moving towards aluminum.

Aluminium is about 3 times lighter than steel per unit volume, but can be made just as strong using certain alloys/shapes/bonding methods.

Because of this, AL parts can be thicker, and thus stronger, than their steel counterparts, all while weighing less.

The first production vehicle to move to an Al frame was the Audi A8 in 1994.

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This allowed Audi to make their full-size car lighter than the competitions (BMW, Mercedes, Lexus...), thus giving them the edge in performance & handling

While Al may seem like a miracle metal for car production, there is a reason not all cars are made from Al... It costs a lot more than Steel.

The most obvious advantage to using aluminum in place of steel in cars is aluminum weighs less.

Audi A8 Audi R8

PRESSURE VESSELES

DRILLING RINGS The application opportunities of aluminium alloy drill pipe (ADP) in

geothermal drilling environments. With the improved development into ultra-

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high energy extraction regions, the geothermal drilling industry is under high

demand and is being tested to drill deeper, faster, and at reduced costs in order

to make geothermal competitive economically and to satisfy energy demands.

The achievement of greater drilling depths requires the advancement of the

drilling industry to address limitations in the weight capacity of the drill rigs

and the temperature limitations of the drilling components. Aluminium alloy

drill pipes (ADP), sometimes referred to as Lightweight Aluminium Drill pipes

(LADP) have been used in the drilling industry in Russia for many years. Due

to ADP’s lightweight and high strength to weight ratio there are several

advantages over conventional steel pipe. These advantages include the use of

larger diameter drill pipe with thicker walls which increase annular flow;

reduced pressure loss inside the drill pipe, resulting in smaller pump

requirements; reduced derrick loads and hook loads due to reduced weight per

length compared to steel and increased buoyancy effects in drilling fluids,

resulting in smaller rigs or greater depth penetrations with current rigs; and

reduced stresses in a number of drilling design parameters. The application

ranges of ADP utilization was studied in regards to temperature limitations,

critical buckling loads and strength of materials, geothermal fluid chemistry,

drilling fluid pressure losses and hydraulics, load comparisons, tool joint

bonding, and economical cost analysis.(2)

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FIG SHOWS DRILLING RINGS

CHAPTER-5Literature Survey

Friction stir welding;

Friction Stir Welding (FSW) is a solid-state welding process created and

patented by The Welding Institute (TWI) in 1991. It is a relatively novel joining

technology, which has caught the interest of many industrial sectors, including

automotive, aeronautic and transportation due to its many advantages and clear

industrial potential. The process adds new possibilities within component design

and allows more economical and environmentally efficient use of materials. The

main advantage of FSW over traditional welding technologies is that joining is

achieved below the melting temperature avoiding deterioration of the material

microstructure and joint mechanical properties often seen in traditional welding,

and adding new dimensions to design and component optimization. Another

important consequence is that the problems related to the working environment

when using traditional arc welding processes, namely air pollution and

ultraviolet light are absent with FSW. Many lightweight materials and in

particular aluminum alloys may be joined by this technique, including the

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aluminum alloys used in the civil engineering (5xxx and 6xxx series), which are

difficult to join by traditional welding techniques [3].

Properties of aluminium5xxx series;5xxx Series. The major alloying element in 5xxx series alloys is mag- cesium.

When it is used as a major alloying element or with manganese, the result is a

moderate-to-high-strength workhardenable alloy. Magnesium is considerably

more effective than manganese as a hardener, about 0.8% Mg being equal to

1.25% Mn, and it can be added in consider- early higher quantities. Alloys in

this series possess good welding characteristics and good resistance to corrosion

in marine atmospheres. However, certain limitations should be placed on the

amount of cold work and the safe operating temperatures permissible for the

higher-magnesium alloys (over ~3.5% for operating temperatures above ~65 °C,

or 150 °F) to avoid susceptibility to stress-corrosion cracking. Figure 2 shows

the relationships between some of the more commonly used alloys in the 5xxx

series. [4]

AA5083-H111 series:Aluminum Alloy 5083 is known for exceptional performance in extreme

environments. 5083 is highly resistant to attack by both seawater and industrial

chemical environments. Alloy 5083 also retains exceptional strength after

welding. It has the highest strength of the non-heat treatable alloys but is not

recommended for use in temperatures in excess of 65 °C.

MECHANICAL PROPERTIES OF AA5083-H111.Tensile Strength 270 - 345 MPa

Hardness Brinell75 HB.

WELDABILITY OF AA5083-111:

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Weld ability – Gas: Average

Weld ability – Arc: Excellent

Braze ability: Poor

Weld ability – Resistance: Excellent

FABRICATION OF AA5083-111:Machinability: Poor

Workability – Cold: Average [3].

GENERIC PHYSICAL PROPERTIES:Density-2.65 g/cm³

Melting Point -570 °C

Thermal Expansion- 25 ×10−6 /K

Modulus of Elasticity- 72 GPa

Thermal Conductivity-121 W/m.K

Electrical Resistivity-0.058 ×10−6Ω.

Discussions regarding FS welds of AA5083-H111:The AA 5083-H111 aluminum alloy, in combination with FSW, is at this

moment the most used alloy in the ship building industry and starting to be also

more present in the field of civil engineering. Because in the civil engineering

field there is not so much information about Aluminum and FSW, it is

necessary to have a good understanding of the process in this direction. So, a

series of research programs are necessary to find some answers for the

combination 5083-H111 + FSW in the field of civil engineering, starting with

simple elements as aluminum plates.

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It is known that the formation of friction stir welded zone is affected by the

material flow behavior under the action of the rotating tool. On the other hand,

the material flow behavior is direct influenced by the material properties such as

yield strength, ductility, hardness of the base material, tool design and FSW

parameters.

Usually, the friction stir welded joints are defect free joints since no melting

takes place during the welding process and the metals are joined in the solid

state due to the heat generated by the friction between the tool shoulder and

components surfaces and flow of metal by the stirring process. The generated

heat has to be high enough to ensure a proper material flow in order to produce

defect free joints. Therefore the process parameters have to be in such manner

combined to produce the proper heat amount for a good joint. [3]

EXPERIMENTAL PROCEDURE:

A FSW tool made of high carbon and high chromium steel (HCHCr) having

straight square (SS) pin profile without draft was used to weld the alloys. The

tool had a shoulder diameter of 18 mm, pin diameter of 6 mm and pin length of

5.7 mm. The FSW tool was manufactured using CNC turning center and wire

cut EDM (WEDM) machine to get a accurate profile. The tool was oil hardened

to 63HRC. Aluminum alloys AA6351-T6 and AA5083-H111 were used in this

work. Their chemical composition is shown in Table 1. Plates with dimensions

of 100 mm× 50 mm × 6 mm were prepared from the rolled plates. AA6351-T6

and AA5086-H111 alloys were respectively kept on the advancing side and

retreating side of the joint line. The FSW line was parallel to the rolling

direction of AA5083-H111 and perpendicular to the rolling direction of

AA6351-T6. This joint choice was made to induce the most severe mechanical

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combination . The dissimilar butt welding was carried out on an indigenously

built FSW machine . Three joints were fabricated at three different welding

speeds of 36, 63 and 90 mm/min. The rotational speed was kept as 950 r/min.

After the welding process, the joints were visually inspected for exterior defects

and it was found that the joints were free from any external defects. A specimen

was cut from the welded plate perpendicular to the FSW line to carry out the

microstructural characterization. The specimen was prepared as per standard

metallographic procedure and etched with modified Keller reagent followed by

Wecks reagent. [5]

Fabrication of FSW Tool:FEW tool made of High Speed steel having a pin profile of straight circular was

used to weld the joints. Tool has a shoulder of diameter 14mm, a pin diameter

of 4mm and a pin length of 4mm.

The design of the tool is a critical factor as a good tool can improve both the

quality of weld and the maximum possible welding speed . It is desirable that

the tool material is sufficiently strong, tough and hard at the welding

temperature. Effect of welding speed on microstructure and mechanical

properties of friction stir welded aluminum alloy was investigated by Sakthivel

et.al. The influence of FSW parameters on the grain size of the stir zone and the

formability of friction stir welded 5083 aluminum alloys was examined by

Tomotake Hirata et.al. The Aluminum plates were friction stir welded at various

rotational speeds (850-1860rpm) and travel rates of 30 to160 mm/min with

welding forces ranging from 2.5 to 10 MPa, using different diameters welding

heads was investigated by Wang and Liv [8]. From these experiments it has

found that dimensions of the welding head are critical to produce sound weld.

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CHAPTER-6ADVANTAGES OF FRICTION STIR WELDING PROCESS

The process advantages result from the fact that the FSW process takes place in the solid phase below the melting point of the materials to be joined.

Friction stir welding can use purpose-design equipment or modified existing machines tool technology.

Low shrinkage, even in long welds excellent mechanical properties in fatigue, tensile and bend tests

No arc or fumes

No porosity

No spatter

Can operate in all position

Energy efficiency

No filler wire required

No gas shielding for welding aluminium

Can weld aluminium and copper of >75mm thickness in one pipe.(6)

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DISADVANTAGES OF FRICTION STIR WELDING PROCES Large forces: order of magnitude 10 KN(backing plate required)

Rigid clamping system needed

Hole at the end if the weld

The problem if the weld gap greater than 10% material thickness

Investigation cost (equipment with high stiffness)

Licence cost

Other welds flams are possible

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CHAPTER-7APPLICATIONS OF FRICTION STIR WELDING

Freezer panels The first commercial application of friction stir welding concerned the

manufacture of hollow aluminium panels for deep freezing of fish on

fishing boats ( Figs 7.1 & 7.2). These panels are made from friction stir

welded aluminium extrusions.

FIG 7.1 shows Sapa FSW panel for pre-pressing of fish blocks before quick freezing. The panel is Welded from both sides

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FIG 7.2 shows Joint design of Sapa's freezer panels

Panels for deck and wall construction Pre-fabricated wide aluminium panels for high-speed ferryboats can be

produced by friction stir welding and are commercially available (Figs (A) & (B)).

The panels are made by joining extrusions, which can be produced in standard size extrusion presses. Compared to fusion welding.

The heat input is very low and this results in low distortion and reduced thermal stresses.

Fig. (A). FSW catamaran side-wall with cut-out sections for windows at Marine Aluminium in Haugesund, Norway

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Fig. (B). Prefabricated FSW panel for half the width of the superstructure of a cruise liner

After welding the panels can be rolled for road transport, as they are stiff

only in the longitudinal direction (Fig(C)). When they can be transported

by ship, they can be stacked on top of each other (Fig (D)).

Fig.(C). Prefabricated FSW panel for a catamaran sidewall, rolled for road transport

Fig. (D). Prefabricated FSW panel for a catamaran sidewall. Straight panel for ship transportation at Marine Aluminium in Haugesund, Norway

(Thomas W M, Nicholas E D, Needham J C, Murch M G, Temple-Smith P and Dawes C J (TWI): 'Improvements relating to friction welding'. European Patent Specification

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REFERENCE

1- Anderson, T.- New developments within the aluminium shipbuilding

industry.

2- Jellison M: Drill Pipe and Drill Stem Technology, Drilling Contractor,

March/April, (2007), 16-22.)

3- www.twi-global.com>friction-stir-welding

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