Super steel with bone-like resistance to cracking under repeated stress created

Scientists have created super steel that is able to withstand repeated stress without cracking. The steel was created by incorporating a laminated nanostructure into it – which gives the metal a 'bone like resistance' to fracturing.

Publishing their study in the journal Science, the team from MIT, the Max Planck Institute in Germany and Kyushu University in Japan, found the metal was significantly more resistant to metal fatigue than traditional steel. The material, they say, could have implications for the automotive and aerospace industries.

Metal fatigue – where it weakens over time as a result of repeated stress – can sometimes result in major failures in structural components of things like aeroplanes, spacecraft, power plants and bridges.

On aircraft, for example, changes to pressure during every flight mean the metal expands and contracts repeatedly. This eventually causes the metal to change shape – which can result in microcracks forming.

To compensate, these structures are normally made with wide safety margins. Because of these safety factors, there are increased costs in production and during the components life.

Inspired by the structure of bone, the team sought to replicate its resistance to cracks. This is largely down to the structure of bone, which has a lattice-like internal structure, so the scientists looked at microstructures that could mimic this in a metal.

They found two types of steel with structures similar to bone and then enhanced these properties by incorporating a laminated nanostructure. In experiments testing their crack resistance, the researchers found their new material was far more resistant to fracturing. Eventually, and under higher initial stress, the steel still cracked – and the team put forward a number of ways this issue could be addressed.

The experiments were carried out a small scale, so commercial applications are not yet feasible – the study authors do not yet know how they could create the steel in quantities needed for industry.

Study author Cem Tasan said: "Economics always comes into it. I'm a metallurgist, and this is a new material that has interesting properties. Large industries such as automotive or aerospace are very careful about making changes in materials, as it brings extra effort and costs."

"For [certain] applications, [the benefits] are so critical that change is worth the extra trouble. This is an alloy that would be more expensive than a basic low-carbon steel, but the property benefits have been shown to be quite exceptional, and it's with much lower amounts of alloying metals (and hence, costs) than other proposed materials."