WPI Researchers Develop Lightweight, Corrosion-Resistant Welds

WPI professor Adam Powell, postdoctoral fellow Kübra Karayagiz (center), and PhD student Qingli Ding prepare to place welds inside the cyclic corrosion test chamber. Photo and caption courtesy of WPI.

Adam Powell, an associate professor of mechanical engineering at Worcester Polytechnic Institute (WPI) (Worcester, Massachusetts, USA), is the principal investigator of a project that aims to produce a new type of welding for cars and trucks that would make the joints between light metal alloys more resistant to corrosion, as well as reduce the weights and extend the lifespans of vehicles.

According to Powell, designing durable, next-generation car joints will involve the use of advanced lightweight materials such as aluminum and magnesium alloys. To that end, Powell’s team is experimenting with friction stir welding, a new welding technique that reduces corrosion in aluminum-magnesium alloy joints. Typically, direct contact between dissimilar metals results in galvanic corrosion, but the team believes that its new welding process will result in durable subassemblies, as well as lighter, more fuel-efficient vehicles.

“We’re trying to show that corrosion can be much less of a problem with this new type of welding,” says Powell. “We think that this process holds a lot of promise and could make a significant impact on energy use in motor vehicles without reducing the lifespan of a car.”

Powell is one of six WPI researchers working on the project, which also received contributions from two national laboratories, Oak Ridge National Laboratory (ORNL) (Oak Ridge, Tennessee, USA) and Pacific Northwest National Laboratory (PNNL) (Richland, Washington, USA), and a global auto parts supplier, Magna International (Aurora, Ontario, Canada). Under the research plan, Magna provides aluminum and magnesium metals to PNNL, which in turn welds the materials and ships the parts to WPI. From there, WPI conducts corrosion and mechanical testing and sends its tested samples to ORNL, which is responsible for advanced analysis of the welds. Finally, WPI runs computer simulations “to try to understand how the corrosion and mechanical fracture work together,” says Powell.

Along with developing computer simulation models, WPI researchers are conducting experiments that rely on a cyclic corrosion test chamber, a device that exposes small sections of weld to various types of corrosion, including salt spray, temperatures that reach up to 140 °F (60 °C), and high humidity. This enables the researchers to determine which welds will best withstand corrosive conditions over an extended period, according to Powell.

Powell and his colleagues have already mapped out the first three years of their research. In year one, they will study the corrosion behaviors of magnesium and aluminum diffusion-bonded joints in the cyclic corrosion test chamber. In year two, they plan on developing computer models that factor both the corrosion of friction stir welded joints and mechanical fracture, and they will refine these models in the third and final year.

The project was awarded a three-year, $1.5 million grant from the U.S. Department of Energy’s Vehicle Technologies Office (Washington, DC, USA), with WPI receiving $750,000 and ORNL and PNNL splitting the remaining funds.

Source: Worcester Polytechnic Institute, www.wpi.edu.