FRICTION STIR WELDING OF ALUMINIUM

METAL MATRIX COMPOSITEHimansu Sekhar Sahu(U13ME086), Mohammad jawed rain(U13ME123) , Narendra Gautam(U13ME134), Navneet Nishant (U13ME136), Pritam Sankar Dhupal(U13ME150)

Mrs.G.Sucharitha,M.Tech, Assistant Professor, Bharath University, Chennai.

ABSTRACTFriction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. The welded process is conducted on varying the welding process parameters, tool rotation speed, welding speed (mm/min), download force (k/N) and tool pin profile. The properties namely defects, microstructure, hardness, tensile and bend behavior on welded plates are studied and compared with the base metal and the results show quality welds could be produced when the tool rotation has the speed of 600-1200 rpm and tensile strength is reduced by about 10 % and the percentage elongation reduced almost half compared to the base metal.

KEYWORDS

Friction stir welding ,Aluminium , tensile, hardness, microstructure

INTRODUCTION

Friction Stir Welding (FSW) is a simple, clean and innovative joining technology for light metals invented by The Welding Institute (TWI), England, U.K. in 1991. Due to the high strength of FSW joints, it allows considerable weight savings in lightweight construction compared to conventional joining technologies. The friction stir welding works on the principle of a rotating pin emerging from a cylindrical shoulder which is plunged between two pieces of sheet and moved forward along the joint line. The material is heated by friction between the rotating shoulder and the work piece surface and simultaneously stirred by the profiled pin leaving a solid phase bond between the two pieces to be joined. Special preparation of the weld seam and filler wires is not required. The process of friction stir welding has numerous advantages over the conventional

welding technologies. FSW process can take place in the solid phase below the melting point of the metals to be joined and is able to weld numerous materials including, but not limited to aluminum, bronze, copper, titanium, steel, magnesium, and plastic. It also yields significantly less distortion than the fusion welding processes, allowing for dramatic cost reductions in many applications. Thus, all the problems related to the solidification of a fused material area voided. Materials classified as difficult to fusion weld like the high strength aluminium alloys used in the aerospace industry could be joined with a minor loss in strength. The small-scale industry can especially benefit from the low investment costs of the mechanical equipment required for Friction Stir Welding. The ability to join

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different aluminium and magnesium alloys offers a great variety of new products.

REQUIRED MATERIALS

This work mainly concentrated on aerospace application, it is advisable to consider properties of the materials in such applicants. The most common and important property is to considered for selection is weight. A lighter aircraft requires less energy and, hence, less fuel to operate. The materials selected are Aluminium and Al2O3.

Aluminium(Metal Matrix): It is cheap and widely used metal in production sector for both industrial and domestic purposes, so developing a proper welding process will only benefit production deparrtments worldwide.Aluminium metal matrix composites are potential materials for various applications due to their good physical and mechanical properties. The addition of reinforcements into the metallic matrix improves the

stiffness, specific strength, wear, creep and fatigue properties compared to the conventional engineering materials.

AluminiumOxide(Al2O3)-(Reinforcement): It is one of the most cost effective and widely used materialin the family of engineering ceramics. The raw materials from which from which this high performance technical grade ceramic is made are readily available and reasonably priced, resulting in good value for the cost in fabricated alumina shapes. With an excellent combination of properties and an attractive price, it is no surprise that fine grain technical grade alumina has a very wide range of applications. Alumina oxide is a chemical compound of aluminium and oxygen with the chemical formula Al2O3.

Chemical properties of AA6061

Aluminium-96.85%, Magnesium-0.9%, Silicon-0.7%, Iron-0.6%, Copper-0.3%, Chromium-0.25%, Zinc-0.20%, Titanium-0.10%, Manganese-0.50%, Others-0.50%

EXPERIMENTAL SETUP

TOOL PREPARATION

H13 Tool: H13 Tool steel is a versatile chromium-molybdenum hot work steel that is widely used in hot work and cold work tooling applications. The hot strength of H 13 resists thermal fatigue cracking which occurs as a result of cyclic heating and cooling cycles in hot work tooling applications. Because of its excellent combination of high toughness and resistance to thermal fatigue cracking and also known as heat checking. H13 is used for more work tooling applications than any other steel. H-13 tool steel which is characterized by high hardenability and excellent toughness.

Aluminium tool- The weighted quantity of Al was melted in an induction type tilting furnace in the

temperature range of 810 C. The alumina particles were preheated in a separate furnace at about 810 C for about 20 minutes before introducing them into the melting furnace. A stirrer (made of Mild steel) is used to obtain an output of 600 rpm. During experimental work, a four bladed 450 angled stirrer was chosen.

Steel tool-Tool steel is a type of carbon alloy steel that is well-matched for tool manufacturing, such as hand tools or machine dies. Its hardness, resistance to abrasion and ability to retain shape at increased temperatures are the key properties of this material.

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PROCEDURE

The friction stir welding a non-consumable rotating tool with a specially designed pin and shoulder is inserted into the abutting edges of sheets or plates to be joined and traversed along the line of joint. The tool serves two primary functions: (a) heating of work piece and (b) movement of material to produce the joint. The heating is accomplished by friction between the tool and the work piece and plastic deformation of work piece. The localized heating softens the material around the pin and combination of tool rotation and translation leads to movement of material from the front of the pin to back of the pin. By using the above tool we did the Friction Stir Welding.

The specimen hence prepared are taken and few of them are selected and cut into two halves and then they are welded back together using friction stir welding process.

Test specimen preparation and required specimen

1.HARDNESS TEST

Hardness Testing Results

Hardness Values: H.V @ 0.5 kg load

Readings LP HAZ Weld HAZ-R R-P

1 71.5, 71.6 70.8,68.5 69.5,71.9 60.6,56.5 45.3,43.9

2 62.7,70.5 57.2,65.0 61.0,58.2 61.1,57.0 60.6,66.9

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1100 120054

56

58

60

62

64

66

68

70

72

WELD HARDNESS

WELD HARDNESS

rpm

wel

d ha

rdne

ss

2.Microstructure Test

Figure .1. Microstructure Test Report

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Figure.2. Microstructure Test Report

ConclusionThe conclusion drawn from the present work are

as follows

1. Different testes performed on friction stir

welded joint specimens of AL alloy with 6%

composition of Al2O3 with different tool

rotational speed and feed.

2. The Ultimate tensile strength of this welded

specimen at 1100rpm is high.

3. The breaking stress and % of elongation of

this weld specimen is high and Hardness is

less at 1100rpm.

4. Hence the overall joint efficiency is good at

1100rpm

5. Micro structure.

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