By Josh Perry, Editor
Researchers from the University of California Los Angeles (UCLA) Samueli School of Engineering created a method for welding an aluminum alloy, AA 7075, which was originally developed in the 1940s and has the strength of steel at one-third of the weight but had been previously impossible to weld together using common processes.
UCLA researchers used nanoparticles to weld a previously un-weldable aluminum alloy. (UCLA Samueli School of Engineering)
When heated, the alloy’s molecular structure broke down, leading to an uneven flow of its aluminum, zinc, magnesium, and copper elements, resulting in cracks in the weld, according to an article from UCLA.
To overcome this challenge, UCLA researchers added titanium carbide nanoparticles to the AA7705 welding wires, which provide the filler material between pieces being welded. The result was welded joints with tensile strength up to 392 megapascals (more than double that of the most common aluminum alloy, AA 6061).
“And according to the study, post-welding heat treatments, could further increase the strength of AA 7075 joints, up to 551 megapascals, which is comparable to steel,” the article added.
Because of the material’s strength at a much lighter weight than steel, it has been used in aerospace applications where it is bolted or riveted together. Finding a method for welding the alloy has the potential to open it up to many other applications, most notably the automotive industry.
“The researchers already are working with a bicycle manufacturer on prototype bike frames that would use the alloy; and the new study suggests that nanoparticle-infused filler wires could also make it easier to join other hard-to-weld metals and metal alloys,” the article noted.
The research was recently published in Nature Communications. The abstract read:
“Lightweight materials are of paramount importance to reduce energy consumption and emissions in today’s society. For materials to qualify for widespread use in lightweight structural assembly, they must be weldable or joinable, which has been a long-standing issue for high strength aluminum alloys, such as 7075 (AA7075) due to their hot crack susceptibility during fusion welding.
“Here, we show that AA7075 can be safely arc welded without hot cracks by introducing nanoparticle-enabled phase control during welding. Joints welded with an AA7075 filler rod containing TiC nanoparticles not only exhibit fine globular grains and a modified secondary phase, both which intrinsically eliminate the materials hot crack susceptibility, but moreover show exceptional tensile strength in both as-welded and post-weld heat-treated conditions.
“This rather simple twist to the filler material of a fusion weld could be generally applied to a wide range of hot crack susceptible materials.”