Man of steel makes breakthrough

Local | Erin Chan 13 May 2020

Local scientists have made a breakthrough in developing a "super steel" that could maintain the material's strength without fracturing.

As scientists and engineers continually seek for ways to improve the performance of steel, a research team at the University of Hong Kong, in collaboration with the Lawrence Berkeley National Lab and University of California, Berkeley, have managed to create a type of steel with 19 percent ductility, 2 GPa yield strength and 102 MPam toughness.

In comparison, conventional steel only has a yield strength and toughness lower than 1.7 GPa and 65 MPam, respectively.

The "super steel" has a unique feature - high-strength induced multidelamination - a mechanism where multiple micro-cracks are formed below its main surface.

These micro-cracks can effectively absorb energy from externally applied forces, resulting in higher toughness resistance.

With raw materials that are already widely used in conventional steel, the "super steel" has a low production cost. In addition, the material shares the same industrial processing route as conventional steel, so it has great potential for mass production. "We attained an unprecedented strength-toughness combination that can address a major challenge in safety-critical industrial applications - to attain an ultra-high toughness so as to prevent catastrophic premature fracture of structural materials," said Huang Mingxin, a mechanical engineering professor at HKU who led the project.

"The breakthrough also changes the conventional view that attaining high strength will be at the expense of deteriorating toughness, which invariably leads to the embrittlement of structural materials and greatly limits their application."

The findings were published in the journal Science last week, in a paper titled "Making Ultrastrong Steel Tough by Grain-Boundary Delamination."

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