Nanostructured Steels

Abstract

Nanostructured metals with grain sizes smaller than 100 nm usually exhibit strengths which can be more than twice higher than their coarse-grained counterparts. The “smaller is stronger” effect is generally understood in terms of the Hall-Petch effect of grain size strengthening, or the capability of grain boundaries to obstruct the motion of dislocations as carriers of plastic deformation. Nanostructured steels take benefit of reductions in the grain size to show improved tensile strength, hardness and in-service properties. The steel nanostructures are usually multi-phase and hierarchical, maintaining or even improving the stress-ductility trade-off. The increasing demands for stronger, tougher, wear resistant and heat-tolerant materials have led to the development of new families of steels where the length scale that controls such properties is in the nanometer range. This chapter provides an overview of the current status of the most technologically relevant bulk nanostructured steels, describing the approaches to metallurgical design, processing routes, mechanical properties, in-use behavior and industrial applications.