Influence of severe plastic deformation on the structure and properties of ultrahigh-carbon steel wire

Ultrahigh-carbon steel wire can achieve very high strength after severe plastic deformation, because of the fine, stable substructures produced. Tensile strengths approaching 6000 MPa are predicted for UHCS containing 1.8%C. This paper discusses the microstructural evolution during drawing of UHCS wire, the resulting strength produced and the strengthening mechanisms active in these materials. Drawing produces considerable alignment of the pearlite plates. Dislocation cells develop within the ferrite plates and, with increasing strain, the size normal to the axis (d) decreases. These dislocation cells resist dynamic recovery during wire drawing and thus extremely fine substructures can be developed (d < 10 nm). Increasing the carbon content reduces the mean free ferrite path in the as-patented wire and the cell size developed during drawing. For UHCS, the strength varies as d(-n), where n is 0.5 to 1. The influence of processing and composition on achieving high strength in these wires during severe plastic deformation is discussed.