The effect of cold rolling with a reduction rate of 95% at room temperature and subsequent aging on the evolution of the microstructure, strength properties and electrical conductivity of the Cu-0.5Cr alloy (wt.%), which is widely used in the electrical industry in the form of strips and ribbons, has been studied. The cold rolling and aging of the alloy was carried out in coarse-grained and ultrafine-grained states after equal-channel angular pressing. The regularities found were used to assess the contribution of various structural parameters to the level of strength properties as well as the electrical conductivity of the alloy in the obtained states.

The results of studying the microstructure, mechanical and electrical properties of the UFG alloy Cu-0.5wt.% Cr, obtained by equal-channel angular pressing (ECAP), followed by cold rolling and subjected to aging, are presented. It was found that, as a result, the average size of the fragmented structure is 160 nm. The results showed that the tensile strength increases with increasing degree of deformation. The maximum strength value of 605 MPa was achieved after a combination of 8 ECAP passes followed by rolling by 95%, while ductility was reduced to 13%. The number of ECAP passes and subsequent rolling practically do not affect the electrical conductivity and is 34-39% of IACS.

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The article studies an influence of temperature of severe plastic deformation (SPD) and post-deformation heat treatment on microstructure, mechanical properties and thermal stability of the Cu-0.5Cr-0.2Zr alloy. The results demonstrate that strength is considerably increased to 900 MPa by high pressure torsion (HPT) at room temperature. Subsequent ageing at 450 °С during 1 hour leads to a decay of solid solution and an allocation of dispersion particles that further incrises strength to 900 MPa, restores electrical conductivity to 70% IACS (International annealed copper standard) and enhances thermal stability of the alloy. When deformation temperature is increased to 300°С, strength is 690 MPa that is lower than in the case of deformation at room temperature that is related to reversion process at deformation. Additional a aging does not lead to an increase of strength characteristics.

Copper and copper alloys are widely used in engineering as structural materials because they have high electrical and thermal conductivity. In connection with the rapid growth of industry, special requirements are imposed on these materials, that is, they must withstand the contact mechanical loads without significant plastic deformation at elevated temperature and have stable high physical and mechanical properties. To improve the combination of strength, electrical conductivity, thermal stability, and wear resistance, low-alloyed Cu-Cr-Zr copper alloys have been subject to severe plastic deformation and aging. It the same time the analysis of the termo-stability of the formed ultrafine grained microstructure and properties is a topic task. In this work, a Cu-0.5Cr-0.2Zr (wt. %) alloy was quenched to form solid solution, equal channel angular pressed and cold rolled with following aging. The microstructure was studied, mechanical and electrical properties were also analyzed. The results showed that the ultimate strength of the Cu-Cr-Zr alloy increases with the degree of deformation at room temperature up to 630 MPa. Heat treatment at 450 ° C for 1 hour led to the precipitation of Cr and Cu5Zr particles, which increases the strength up to 660 MPa, which is 2.5 times greater than the initial state. At the same time, sufficient electrical conductivity of 70% IACS is maintained. The thermal stability of the microstructure and properties of the alloy are investigated. The reinforced alloy maintains stable the microstructure and microhardness at 450 ° C for at least 5 hours. The change in microhardness is no more than 10%. That is in agreement with the requirements of industry.

The effect of equal-channel angular pressing (ECAP) on the strength and electrical conductivity of low-alloyed Cu-Cr-Zr alloys to identify conditions for the formation of states with high strength and electrical conductivity is considered. The increase in the content of alloying elements does not increase the strength of the alloys in the initial quenched state. After ECAP, their strength is increased by dislocations. It is shown that after ECAP of quenched samples, their specific resistances remain almost unchanged due to the increase in the length of the grain boundaries, the volume fraction of small particles of secondary phases and the segregation of alloying atoms from the matrix.

Abstract. The paper studies the effect of the combination of ECAP and cold rolling on the structure, mechanical properties and coefficient of friction of low-alloyed bronzes. It is shown that the use of ECAP together with rolling leads to the formation of a UFG structure and an increase in strength characteristics, while the coefficient of friction is increases. Subsequent heat treatment results in additional hardening by the separation of fine particles, which also reduces the coefficient of friction.