The non-consumable tool is turned and inserted into the joint between two work parts. It has a profiled probe and shoulder. The substance then heats up and softens as it moves along the joint line. This plasticized material, which is mechanically combined to form a solid phase weld, is likewise contained by the shoulder.
What are the Applications?
Whether cast, rolled, or extruded, aluminium alloys of all grades are joined via this technique most frequently in the industry. According to the alloy grade and machine capacity, FSW has been demonstrated to weld aluminium alloy butt joints with a thickness of 0.3mm and 75mm in a single pass.
Magnesium, titanium, copper, nickel, and steel alloys are some other materials that have been coupled using FSW. Plastics and metal matrix composites (MMC) have also been investigated. Additionally, it has been demonstrated that this method can combine other combinations of these materials, including steel and aluminium.
FSW has been applied in various fields, including EV battery trays, from electronics to shipbuilding, rail, and aerospace.
Mechanical Properties and Microstructure
Friction stir welding has produced aluminium alloys with greater mechanical properties than other welding techniques, such as arc welding.
A weld nugget, a thermo-mechanically affected zone (TMAZ), and a heat-impacted zone are typically the three primary microstructural regions of FSW concerning its mechanical qualities (HAZ).
The microstructural properties of the weld nugget and the TMAZ are considered independently even though they are both “thermomechanically affected zones.” This is because the TMAZ does not undergo dynamic recrystallization, while the weld nugget does. However, the type of material and the processing circumstances impact the precise composition and extent of the microstructural composition in these zones. These, for instance, may change based on variables like the welding conditions and the design of the FSW equipment being utilized.
What are the Advantages?
Comparing friction stir welding to traditional arc welding procedures reveals some benefits. These consist of the following:
- As a solid-state welding process, FSW is a largely defect-free joining method with no hot cracking, porosity, or solidification cracks
- Due to the lower temperatures, there is a reduction in shrinkage and distortion in the material being joined
- No filler materials, flux, or shielding gas requirement for aluminium alloys
- FSW is environmentally friendly as it produces no fume, spatters, or UV radiation
- Uses machine tool technology, making the process easy to automate, highly repeatable, and reducing the need for skilled welders
- Can work in any position
- Good mechanical properties, which for aluminium alloys typically equal or exceeds those obtainable by competing processes
- Energy efficient
- Able to join many ‘non-weldable’ aluminium alloys, such as those from the 2xxx and 7xxx series
- No requirement for special edge preparation in most applications
What are the Disadvantages?
Even though friction stir welding has a lot of benefits, there are some drawbacks to the method. These consist of the following:
- Exit hole left after withdrawing tool from the materials to be joined; however, this can usually be accounted for in the design of the part or by using run-on/off tabs
- The need for significant downforce and traversing forces means that clamping on the parts to be joined is more substantial than for arc welds
- Gaps between the parts to be joined need to be controlled, as no filler material is used in the process
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