Possibilities for industrial application of ultrafine grained copper alloys

Even being relatively costly, copper and copper-based alloys are indispensable where high electrical and/or thermal conductivity are required of a constructional alloy.

In modern engineering applications high conductivity should often be combined with high strength, fatigue endurance and other mechanical properties not intrinsic for copper.

Energy, automobile, vehicle and aerospace industries, nuclear engineering and thermal energetics specify enhanced demands to the combination of mechanical and physical properties of copper-based alloys.

For example, resistance welding electrodes, which are widely used in the industry, must possess high electrical conductivity and withstand a cyclic loading at elevated temperatures. Application of high-strength thermal conductors, cables, parts of electric power plants, electric motors, generators, various heat exchangers is very topical.

A material for coils of high-field constant magnets should combine high conductivity to minimize the heat production with the mechanical strength sufficient to withstand the Lorentz forces.

Precipitation hardening and cold rolling are conventionally used for hardening of Cu-based alloys. At the same time a vast bulk of research results shows that refining of crystalline structure of precipitation hardened copper alloys provides best mechanical characteristics with high thermal stability, preserving sufficiently high electrical conductivity. Severe plastic deformation techniques, which allow obtaining high strength characteristics for copper alloys, were developed in the Institute of Physics of Advanced Materials. For the sake of comparison, the data on physical and mechanical characteristics of copper alloys after conventional treatment techniques and after various combinations of severe plastic deformation techniques are presented.

In UFG materials the main structural strengthening feature is a high density of grain boundaries, these materials demonstrate behavior quite different from conventional cold-worked materials, strengthened mostly by dislocation pile-ups. Better mechanical and thermal stability, higher ductility and an ability to absorb large doses of neutron radiation without considerable recovery and other adverse effects are among the differences. The last property is of particular interest for aerospace industry and nuclear engineering and, first of all, for thermal energetics.

Now, when reliable SPD technologies for production of bulk UFG metals are available, material performance for many important applications may be considerably improved.

Some physical and mechanical properties of copper-based alloys after various treatments of semi-products

Resistance welding electrodes

Contactors in power units

High-field magnets

in nuclear reactors

Semiproducts from copper alloys Cu-1%Cr and Cu-1%Cr-0.2%Zr, processed by the combination of different SPD techniques