WMG's International Manufacturing Center at WMG, University of Warwick. (Credit: University of Warwick)A research breakthrough from the Warwick Manufacturing Group at the University of Warwick has led to the ability to process high-strength, lightweight steels on an industrial scale.
Brittle phases occur during the production of certain steels that limit their ductility and make them difficult to roll. But a new processing route incorporating higher annealing temperatures (900 to 1200 degrees Celsius) allows low-density steel-based alloys to be produced with maximum strength, without losing durability and flexibility. It addresses a challenge that’s been largely impossible to surmount until now: strengthening lightweight steels through current processes makes them less flexible, and therefore less marketable.
The WMG researchers used simulation and experimentation to control the undesirable brittle phases, allowing the steels to retain their ductility. They worked with two lightweight steels, Fe-15Mn-10Al-0.8C-5Ni and Fe-15Mn-10Al-0.8C. Specifically, they were able to remove the kappa-carbide (k-carbide) phase from production, and manage the B2 intermetallic phase. The latter formed in a disk-like, nano-sized morphology, as opposed to the coarser product that forms at lower temperatures.
The research could lead to safer and greener cars. More malleable steels allow manufacturers to form car parts into more streamlined shapes; vehicles made of stronger and lighter materials are safer for drivers, emit less CO2 and consume less fuel.
"Most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off,” says Dr. Alireza Rahnama, lead author of a paper published in a recent edition of Acta Materialia. ”This paper studies the kinetics and thermodynamics of microstructural evolution of lightweight steels through simulations and experiments and proposes a mechanism to achieve higher strength and larger ductility; a method that can be readily adopted by industry."
The paper is co-authored by Dr. Hiren Kotadia and Prof. Sridhar Seetharaman. The project is funded by the WMG Catapult High Value Manufacturing (HVM) center.
