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New welding technology takes hi-end aluminium frames to next level

A team of the University of California (UCLA) has developed a new welding technology for high quality aluminum. It takes alloy frames to the next level as it offers the possibility to weld AA7075 alloy. This brings superlight and superstrong frames able to compete with the ones made of carbon. Does it offer opportunities for a new generation of e-MTBs?

New Welding Technology Takes Hi-End Aluminum Frames To Next Level
Grad student Maximilian Sokoluk (left), laboratory mechanic Travis Widick and Prof. Xiaochun Li, with a prototype welded AA7075 bicycle frame.

Aluminum 7075 series is a fairly common material used in the bicycle industry. With great strength to weight ratio it’s a popular choice for all sorts of components. However, not for frames. Why? Because it’s regarded as an un-weldable alloy. This is however about to change thanks to a team from UCLA. Their innovation could boost the use of high-end aluminium frames for all sorts of hi-end bikes as well as e-MTBs and Cargo bikes.

Phase segregation
Professor Xiaochun Li and his team from the Department of Mechanical and Aerospace Engineering of UCLA, developed the new technology for AA7075 alloy welding. They found a simple, but clever as well as efficient solution for the problems associated with welding 7075 alloy. These problems lies in the fact that when the metal is heated, the aluminum, zinc, magnesium and copper of which it’s composed flow unevenly. The phenomenon is known as phase segregation, and as a result of it, cracks form along the length of the weld.

Filler rods with TiC nanoparticles
The welding technology Professor Xiaochun Li and his team invented for making, for instance, hi-end bike frames made of the named high-quality aluminum is based on the use of filler rods with TiC (titanium carbide) nanoparticles. This prevents the hot cracks, typically associated with the welding of 7075/7050 alloys. In fact the welded joints show amazing strengths. They show a tensile strength of up to 392 megapascals – by contrast, the commonly-used 6061 aluminum alloy has a weld strength of 186 megapascals. What’s more, it is believed that post-welding heat treatments could boost the strength of the 7075 welds up to 551 megapascals, which is on par with the weld strength of steel.

The application of this new technology requires no additional investments. According to Professor Li the filler rods with TiC nanoparticles can be used with existing welding tools.

Direct competition to carbon
Alloy AA7075 is almost as strong as steel but weighs about one third. Such strength to weight ratio offers solutions for all sorts of vehicles like road bikes as well as all electric bike categories where lower weight means lower energy consumption. According to the UCLA Professor the new welding technology not only closes the gap between AL6061 and carbon frames, but offers direct competition to carbon fiber technology in the bicycle industry.