South China Morning Post has reported that a Chinese-led team of scientists from Northeastern University in Shenyang, Shenyang National Laboratory for Materials Science and Jiangyin Xingcheng Special Steel Works in eastern China, as well as the Max Planck Institute for Iron Research in Germany, have developed a new type of steel that is ultra-strong yet stretchable, potentially overcoming a tough challenge in steelmaking. According to the team, a piece of the steel the size of a fingernail can bear the weight of a 2-tonne car without fracturing, and the ductile metal can also be stretched by 18-25%. Researchers said that the material would have applications in the vehicle, aerospace and machinery sectors, where it could be formed into complex shapes and absorb high energy from the impact of a collision. Creating ultra-tough steel that can also be extended has been a major challenge for scientists because strength and ductility are usually mutually exclusive. For the study, the researchers came up with a new hierarchical nanostructure design, aiming to produce steel with both characteristics. To create it, they forge melted raw alloyed material at 650 to 800 degrees Celsius and let it air cool, during which the special structure formed. They then used liquid nitrogen, which has a temperature of minus 196 degrees Celsius, to cool it down further, before heat treating it at 300 degrees Celsius to improve its stability. Northeastern University’s State Key Laboratory of Rolling and Automation postdoctoral researcher Mr Li Yunjie said “It was a much simpler process than that used to make conventional ultrahigh-strength steels, which are rolled to form thin plates or sheets. It produced 2 gigapascal-strength steel, which is almost the highest tensile strength in steels. Manufacturing method could reduce the cost of producing a tonne of steel by about CNY 510 (USD 75) and cut carbon emissions by more than 100kg coal equivalent per tonne.” Mr Li also said “The future of producing the steel at a tonnage scale is promising. The associated processes proposed in our study, especially the forging procedures, have long been widely used in many companies and production environments to produce parts like axes, ship shafts and so on. There is already large-scale ship shaft with a tonnage scale based on the forging. Our process is consistent with its preparation with only a few adjustments in some process parameters. Industrial heat treatment platforms could be used to treat the forged products, followed by cooling and tempering using large-scale deep cold boxes and furnaces.” The team is now working on practical use of the steel by looking into specific application scenarios and evaluating its performance in other areas such as metal fatigue and fracture toughness.