Searching for the perfect steel

Malleable, elastic, and at the same time, strong – these are the sought-after properties for steel and other alloys.

Working with a research team in South Korea, researchers at KTH Royal Institute of Technology have developed a theory that describes how metals’ plasticity can evolve and change in the pursuit of the perfect steel.

The development of optimal steel and other alloys, that is, materials with metallic properties consisting of two or more elements, is central to materials research.

Now, the new theory has potential to revolutionize the steel industry. Levente Vitos, professor in applied materials physics and leader of the research group’s work at KTH, says that their theory is based on quantum physics and how different elements in metals interact and influence each other at the atomic level.

Specifically, the team researched and found the mechanism behind what materials scientists call, “plastic deformation”, or the permanent change that happens in the shape of a material in response to applied force. Vitos gives a typical example: “If you strike the body of a car hard enough, it causes a dent, that is, there is a plastic deformation.”

Existing theories fail to fully explain plasticity, and this lack of a deeper understanding of plasticity has until now been an obstacle to creating the perfect steel, Vitos says.

But now the Swedish and South Korean researchers have found the secret – at the atomic level – for creating an extremely stretchy, strong and malleable material.

The explanation for these unique and sought-after properties lies in the plasticity of the alloy, and is caused by so-called twinning and stacking faults in the atomic structure.

“Through our research, it is possible to design new alloys with optimal mechanical properties,” says Börje Johansson, professor of applied materials physics in the Department of Materials Science at KTH.

The scientists say that the environmental benefits of their theory would include the ability to build ultra-light vehicles and aircraft, which would consume less fuel on account of their reduced weight.

“Because of our serious environmental and energy problems, we need to develop appropriate materials with specific physical properties,” Vito says. “Eventually we will be able to create ultra-light, more crashworthy cars, or airplanes that weigh half of what they weigh today. These can reduce energy consumption significantly.”

Johansson says the research can also lead to better and increased production in the steel industry.

Transforming theoretical models to practical applications is facilitated by the team’s close cooperation with industry. For example, Sandvik is a strategic partner to KTH.

“Of course, materials are developed all the time in the industry; but with the help of the theory and the method we have developed, these can be done on a larger scale and more completely,” Johansson says.

Vitos and Johansson believe that their model will be standard in most R&D departments in the steel industry within a few years’ time.

Jill Klackenberg