Friction Stir Welding in Aerospace

Aerospace is where FSW earned its production credentials. The high-strength 2xxx and 7xxx airframe alloys are effectively unweldable by fusion processes — which is why aircraft were riveted for a century — but they friction stir weld reliably, with joint strengths above 90% of parent in thin sections and no porosity or solidification cracking to inspect for.

Where FSW is used today

Launch vehicle structure

Every major Western launch programme now friction stir welds its propellant tanks: NASA adopted FSW for External Tank and later SLS/Orion barrel, dome and circumferential welds in Al-Li alloys (the Artemis programme’s Orion crew module is FSWed), Ariane 5 and 6 tank structures are FSW, and SpaceX built Falcon 9’s tanks around the process from the outset. The driver is the same everywhere: fusion welds in 2xxx-series alloys leak and crack; stir welds do not.

Airframe structure

The Eclipse 500 business jet certified FSW in place of thousands of rivets in cabin and aft-fuselage assemblies — faster than riveting, lighter, and FAA-accepted. Stiffened panels, floor structures and fuselage skins remain the reference applications for replacing fastening with a continuous, hermetic, parent-metal joint.

Thermal and cryogenic hardware

Avionics cold plates and liquid-cooled chassis (see thermal management), and cryogenic tanks — FSW’s freedom from porosity matters doubly when the contents are liquid hydrogen or oxygen.

Where the research is heading

• Hydrogen flight. Circumferential FSW of thin-walled, flow-formed and spun domes for liquid-hydrogen storage — joint design, internal reaction tooling and cryogenic fracture performance are active development topics across UK and EU programmes.
• Thin-section and refill spot welding. Stationary-shoulder FSW for distortion-critical skins, and refill friction stir spot welding as a flush, hole-free replacement for rivets in skin-stringer joints.
• Titanium and high-temperature alloys. Tool materials (PCBN, W-Re) now make Ti-6Al-4V and nickel superalloy stir welds practical; the research focus is tool life and process windows at production rates.
• Qualification by data. In-process monitoring of forces, torque and temperature as a route to reducing the NDT burden — moving from inspecting quality in to recording it weld by weld.