It’s a frustrating fact that whenever you try to improve materials like steel, you end up introducing new weaknesses at the same time. It’s a balancing act between different properties. Now, engineers have developed a new type of “super steel” that defies this trade-off, staying strong while still resisting fractures.

For materials like steel, there are three main properties that need to be balanced – strength, toughness and ductility. The first two might sound like the same thing, but there’s an important difference. Strength describes how much of a load a material can take before it deforms or fails, measured in Pascals of pressure. Toughness, meanwhile, measures how much energy it takes to fracture a material.

For reference, glass has relatively high strength but low toughness, so it’s able to support quite a bit of weight but it doesn’t take much energy to break.

And finally, ductility is a measure of how easy it is to extend or elongate a material into different shapes. Unfortunately, improving one of these three properties tends to lessen another. Boosting strength, for instance, often makes a material less tough or ductile.

Liu Li (left) and Huang Mingxin (right), demonstrating the new super steel/University of Hong Kong

 

But now, researchers at the University of Hong Kong and Lawrence Berkeley National Labs (LBNL) say they’ve managed to produce a type of steel that has high-level performance in all three properties. And they boldly call it “super steel.”

The new material has a yield strength resistance against deformation of around 2 GigaPascals, a fracture toughness of 102 MPa-m½, and a uniform elongation of 19 percent. The team says this makes the super steel stronger and tougher than the Grade 300 maraging steel used in aerospace engineering – and the new steel only costs about 20 percent of the price to manufacture.

The super steel is made using a new deformed and partitioned method (D&P), and it gets its toughness from a unique design feature. When a fracture appears at the surface of the material, multiple tiny cracks form below it. These micro-cracks go on to absorb the energy from external forces, which prevents the main fracture from spreading too quickly.

 

The new super steel's fracture resistance is tested

University of Hong Kong

The team says that the new super steel could find use in high-strength bridge cables, bullet-proof vests, and car springs, among other applications.

“We have made a big step closer to industrializing the novel super steel,” says Huang Mingxin, lead author of the study. “It demonstrates a great potential to be used in various applications including superior bulletproof vests, bridge cables, lightweight automobile and military vehicles, aerospace, and high strength bolts and nuts in the construction industry.”

The research was published in the journal Science.

Source: University of Hong Kong

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