Development of severe plastic deformation methods for the production of contact wires from a Cu-Zr alloy for high-speed railways

Zirconium is, like chromium, one of the most promising alloying elements. Microalloying with these elements enables increasing significantly not only the mechanical characteristics of copper alloys by cold deformation methods, while preserving a high electrical conductivity, but also imparting hot-strength properties. At room temperature, zirconium bronze is slightly inferior to chromium bronze in terms of strength characteristics, but it has a higher electrical conductivity and ductility. This set of properties determines the operational efficiency of wires. Another important parameter is the wear resistance of wires. Taking into account the operational restrictions related to wear, amounting to 20% of the wire's cross-sectional area, wires can be strengthened not across the whole section, but with a gradient, i.e. with a stronger surface layer and a weaker core. This will enable providing an enhanced wear resistance and strength of a wire and further increasing its ductility and bending fatigue limit. One of the methods to produce such properties is the method of rotary active alternating bending, which enables, in the conditions of multi-cycle processing, accumulating a high level of strain predominantly in the surface layers of wires. In this work, we present the study of this method with respect to the formation of a gradient-type structure in the samples of a Cu-Zr alloy, with the use of computer and full-scale modeling. (paper)