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Friction Stir Welding of Aluminium Alloys

Friction Stir Welding Of Aluminium Alloys

Friction Stir Welding (FSW) is a ­welding process that was invented, developed and patented in Cambridge, by The Welding Institute (TWI) in 1991. FSW is a solid-state joining process where a third body tool is used to join the two facing surfaces. Heat is generated between the material and the tool, leading to a softened region around the friction stir welding tool. The two pieces of metal are then mechanically intermixed at the place of the joint, meaning the softened metal can be joined via mechanical pressure.

fsw

The process is primarily used on aluminium; most often extruded aluminium. This procedure can also be exploited on structures that require superior weld strength without heat treatment after the weld is complete.

Since its inception in the early 90s, the research and study behind this radical joining process has greatly increased; with many companies and research institutes investing heavily in FSW. Before the end of 2007, The Welding Institute had issued 200 licences for use and the number of FSW related research papers since then has grown exponentially.

FSW & Aluminium Alloys

Due to the benefits and potential advantages over processes such as arc welding, friction stir welding has sparked interest in many areas of industry that work with aluminium. FSW allows you to produce long lengths of welds in aluminium without the need to melt the base material. This eliminates the possibility of solidification cracking and provides important metallurgical benefits when compared to other, more conventional welding methods.

Powerstir Friction Stir Welding

This process also offers low levels of distortion that is often associated with lower heating during the welding procedure. Porosity issues are also eliminated and minimum edge preparation is required when it comes to friction stir welding aluminium alloys.

Advantages of Friction Stir Welding For Aluminium Joining

There are many advantages to friction stir welding aluminium alloys, including:

  • The process can be applied to all major aluminium alloys.
  • FSW does not rely on specialised welding skills.
  • Issues such as hot cracking, porosity and element loss are avoided.
  • No requirement for shielding gas or filler wire.
  • FSW is remarkably tolerant to poor quality edge preparation.
  • The process is extremely flexible.
  • It allows for superb mechanical properties, competing strongly with welds made by other processes.
  • FSW is completely workplace friendly.

The Future of Friction Stir Welding

The application of friction stir welding has primarily focused on aluminium alloys. However, the process is also well developed for both magnesium alloys and copper alloys. Work is also under way to develop this technique and technology for materials such as steels, titanium alloys, nickel alloys and even molybdenum. However, welding these materials must take place at much higher temperatures and so further research is needed to improve the feasibility, performance and longevity of tool materials.

In addition to this, more work and research must go into the use of friction stir welding on dissimilar aluminium alloys. So far most of the research and work we know today has focused on welding similar materials. The economic and environmental push to use lightweight materials in motor vehicles has been largely responsible for the research conducted in joining aluminium alloys to other materials. This includes aluminium to magnesium, aluminium to steel, aluminium to copper and aluminium to metal matrix composites.

Visit PTG’s Powerstir FSW page for more information.

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