Steel just had to be strong in the old days, but builders and engineers are now demanding more out of the material. They want a metal that is tough, but also flexible and lightweight, and are therefore turning increasingly to titanium alloys. Researchers have developed low-density steels by alloying iron with aluminum, carbon, and manganese, but these products are often weak or brittle. Scientists led by Hansoo Kim of the Graduate Institute of Ferrous Technology, in South Korea, have shown that a little nickel goes a long way toward making low-density steel that is both strong and flexible (Nature 2015, DOI: 10.1038/nature14144). The team demonstrated that nickel catalyzed growth of iron-aluminum microparticles and nanoparticles at defect sites in a low-density, aluminum-rich steel when it was annealed at around 900 °C. These brittle particles strengthened the steel, but because they were small and dispersed, they did not compromise its pliability. Kim says the steel’s properties are better balanced than those of titanium alloys, adding that the new alloy is also less expensive and could thus be attractive to the automobile and aerospace industries.