Friction stir welding is A process by which thermoplastic materials are

softened and welded together with heat produced by friction. Friction stir welding is used particularly for joining aluminum alloys, the technology provides significant advantage to the aluminum extrusion industry . the maximum temperature usually lies between 425 and 500°C

FWS

Spin weldingLinear Friction

WeldingFriction Surfacing

The two pieces of metal to be welded together are placed into the two holders. The rotating holder is connected to a flywheel. The rotating piece is spun up to a high speed by a motor and then forced against the stationary piece. The force remains applied for a while after rotation stops, to allow the pieces to set.

Linear friction welding involves two holders, one of which vibrates and one of which remains stationary. The two pieces of metal to be welded together are placed into the two holders. The vibrating holder vibrates and is forced against the stationary piece. The piece must be kept under constant pressure for the joint to set.

Friction surfacing is a method of attaching a thin layer of one substance to another. A rod made of the material to be coated is spun under pressure. This creates a plasticized layer in the rod that is passed over the material to be coated. The plasticized material is deposited on the base material and fuses to it, creating the desired thin layer.

• As a solid state process it can be applied to all the major Al-alloys and avoids welding process problems.

• No shielding gas or filler wire is required

• excellent mechanical properties

• No Fusion No Thermal contraction No distortion

• fewer welding passes are required (high thickness /pass)

• Exit hole left when tool is withdrawn

• Large down forces required (Clamping Force)

• Less flexible than manual and arc processes ( not in Site)

• difficulties with thickness variations and non-linear weld

• Often slower traverse rate than some fusion welding techniques

Apps

Low Temperature Welding

Liquid Hydrogen and Oxygen Cylinders

Shelters Fuel's Tank

High Temperature Welding

Automobiles and Airplanes Industry

Railways

TiZnMnCrCuFeSiAlloyingelement

0.020.060.17 0.28 0.33 0.620.9Wt%

Poison ratio Modulus of Elasticity(GPa)

Melting point (C)

Density (g/cm3)

property

0.3370-805802.7 AA6061

Parameters

Forces Rotational Speed Feed Tool

• A downwards force: is necessary to maintain the position of the tool at or below the material surface

• The traverse force : acts parallel to the tool motion and is positive in the traverse direction (result of the resistance of the material T F )

• The lateral force : may act perpendicular to the tool traverse direction and is defined here as positive towards the advancing side of the weld

• Torque is required to rotate the tool : the amount of which will depend on the down force and friction coefficient

• The tool is tipped with a probe, called a pin or nib, which typically rotates within the range of 200 to 1400rotations per minute (rpm)

• he traverse rate of the tool along the joint line is between 20 to 120 millimeters per minute (mm/min)

• The tilt of the cylindrical tool can have major effects on the welding process. A general range for tool tilt is between 2 and 4 degrees

• The tool shape effect the mechanical properties of the alloy

Nugget Zone (SW – DXR) :

1. The grains within the stir zone are roughly equiaxed and had magnitude smaller than the grains in the parent material

2. A unique feature of the stir zone is several concentric rings which is similar to "onion-ring" structure.

3. the dislocation density is very low but has a large toughness

TMAZ :

1. occurs on either side of the stir zone

2. Higher strength than the stir zone and lower deformation

3. Lower recrystallization than the stir zone

HAZ (heat affected Zone ):

1. No deformation

2. Had the poorest mechanical properties

3. Same of Base material Grains ,because the friction heat produced during the FSW is not enough to result any change

Elongation, %Proof stressTensile Strengthproperty

1.685150HAZ

5.388179TMAZ

14.496250SWZ

0

50

100

150

200

250

300

HAZ TMAZ DXR

UTS

PS

Elongation

Residual stresses arise from the accumulation of misfit between the weld region and the remaining plate. There are a number of means by which the misfit, and hence the residual stresses, can be manipulated:

1. thermal tensioning2. mechanical tensioning3. subsequent processing treatments.

Because of the high temprature and the chemical composition of the alloy, many types of corrosion appear :

1. (crack stress corrosion) precipitation of a network of Cu rich intermetallic at grain boundaries

2. ( Localized corrosion ) this type affect TMAZ at LT and HAZ at HT

3. galvanic corrosion in the nugget

4. potential Stress (Residual ) corrosion (HAZ)

1. Surface Treatment ( Coating )

2. Post heating and pre heating processes

3. Heat Treatment

4. Laser Surface melting