Abstract
The quantitative concentration of alloying elements in low-alloyed copper alloys is an important factor in forming electrical and mechanical characteristics. It is known that severe plastic deformation is accompanied by both a substantial refinement of the structure and changes in the kinetics of phase transformations during the deformation and the post-deformation thermal treatment. This paper presents the results of a comparative analysis of the Cu–0.2Cr and Cu–1.1Cr alloys subjected to equal-channel angular pressing at room temperature. The analysis was performed for the grain structure, solid solution, and second-phase particles using transmission electron microscopy, scanning electron microscopy, X-ray crystal analysis, and the small-angle diffraction method. It was found that the level of structure refinement and mechanical characteristics after equal-channel angular pressing was almost the same for both studied alloys. Post-deformation aging of the Cu–0.2Cr alloy leads to the development of polygonization and re-crystallization within it. The aging of the Cu–1.1Cr alloy shows a better thermal stability than that of the Cu–0.2Cr alloy. In the Cu–1.1Cr alloy, after aging, in comparison with Cu–0.2Cr, a denser-packed ensemble of fine particles with an average size of 54 ± 2 nm is formed. In this case, the average size of fragments is 270 ± 15 nm and the ultimate tensile strength reaches 485 MPa.
Highlights
Copper has a high electrical conductivity but a low strength, which limits its area of application
It has been found that the Zr content on the order of several hundredths has a beneficial effect on the strength of a Cu–Cr alloy, but the electrical conductivity of an alloy is somewhat reduced
It has been found that zirconium reduces the diffusion activity of chromium in an alloy, which contributes to the formation of smaller dispersed particles
Summary
Copper has a high electrical conductivity but a low strength, which limits its area of application. One of the approaches to increase the material strength is its alloying. This leads to a reduction of electrical conductivity. Low-alloyed precipitationhardening bronzes of Cu–Cr system demonstrate a good combination of strength and conductivity [1,2,3,4,5]. The strength of a ternary system alloy can exceed 500 MPa, depending on the method of deformation processing and the accumulated strain. In this case, the electrical conductivity is about 80% IACS (International Annealed Copper Standard) [2,5,6,7,8,9,10]
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