With the use of nanoparticles, previously “unweldable” high strength aluminum alloy is now “weldable” and may see increased usage.
Aluminum alloy 7075 (AA7075) is quite an impressive material: it is nearly as strong as steel with just a third of its weight. Due to its high strength-to-density ratio, AA7075 is a preferred material for applications that require strong, but light materials.
However, manufacturers typically prefer to use materials that are easy to weld or join together to reduce production cost. Subjecting this alloy to fusion welding causes the welded part to crack.
The reason for this is that when AA7075 melts during fusion welding, the alloy’s component elements (aluminum, copper, zinc, and magnesium) undergo uneven flow. This phenomenon results in cracks along the weld.
Recent researches have found that introducing nanoparticles to solidification processes like arc welding and casting have improved the quality of the final product. “Nanoparticles are not only known to enhance the properties of metal matrices; they also strongly influence grain growth and solid fraction of alloys during solidifying, along with the viscosity and thermal properties of the melt,” the authors of the study noted.
Engineers at UCLA Samueli School of Engineering applied these observations to AA7075 and obtained positive results.
The weld displayed an ultimate tensile strength of 392 megapascals. After heat treatment, it increased to 551 megapascals, which was about 96% of the welded alloy’s strength.
In a statement, Xiaochun Li (project lead investigator) said that “the new technique is just a simple twist, but it could allow widespread use of this high-strength aluminum alloy in mass-produced products like cars or bicycles, where parts are often assembled together.” Li added that “companies could use the same processes and equipment they already have to incorporate this super-strong aluminum alloy into their manufacturing processes, and their products could be lighter and more energy efficient, while still retaining their strength.”
Its excellent strength and capability to withstand high stress make this alloy widely used in the aerospace and military industries. This recent development in welding AA7075 may result in its increased use by other industries like construction, automobile, shipbuilding, and specialty goods.
The full research article can be read here.