An alloy made of several different metals can occasionally develop flaws and structural instability. Researchers at the Swanson School of Engineering at the University of Pittsburgh are now using these imperfections to improve alloys, make the material stronger and more flexible at the same time.
Researchers have found a way to make metastable alloys that can overcome the well-known trade-off between strength and ductility. This makes it possible to make alloys that can be used in many different ways.
Wei Xiong, assistant professor of mechanical engineering and materials science, whose Physical Metallurgy and Materials Design Laboratory conducted the study, said, “Our work is showing how we can intentionally introduce imperfections in an alloy to improve alloys make it stronger while maintaining the ductility, or flexibility, of the material. We are working on ways to make materials that can be used in nuclear energy, oil or hydrogen transportation, navy ships, airplanes, and other places where strong but flexible materials are needed.
In this study, transformation-induced plasticity (TRIP) and twinning-induced plasticity, two mechanisms for metastability engineering that might be exploited to produce strong, ductile alloys, are examined (TWIP). TRIP and TWIP use flaws in the material that are caused by changes in the microstructure caused by pressure to make the material stronger.
“Consider the strength and malleability of plastic compared to glass. Although it is not as robust, plastic is far more malleable and pliable, allowing you to bend it with your hands “said Xiong. “Though glass is more durable than plastic, it is also less flexible and will shatter if you attempt to bend it. We are attempting to address this trade-off by using alloys that are both strong and ductile.
In order to complete their study, Xiong collaborated with researchers from the Illinois Institute of Technology, Northwestern University, and lead author Xin Wang, a graduate student in the Physical Metallurgy and Materials Design Laboratory.
The team’s density functional theory calculations in conjunction with the CALPHAD modeling produced essential knowledge that may be used to create metastable alloys with TRIP/TWIP for improved strength-ductility synergy. Concentrated alloys like steel and nickel can also be used.
In order to foresee instability and use faults to further boost strength and elongation, Wang added, “We need to understand the unstable microstructure. The material that is made acts as its own reinforcement, getting stronger when it is bent.
