Source: https://lettersonmaterials.com/en/Readers/Article.aspx?aid=8867
Timestamp: 2019-04-20 10:10:55+00:00

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The effect of high strain-rate (100000 s-1) deformation by the method of dynamic channel-angular pressing (DCAP), annealing and quasi-static severe plastic deformation (SPD) by sliding friction on the evolution of structure and properties of a low-alloyed dispersion-hardened Cu–Cr–Zr alloys have been investigated. It is shown that the alloying of copper with chromium (0.09–0.14%) and zirconium (0.04–0.08%) microadditions changes the mechanisms of submicrocrystalline (SMC) structure formation and elastic energy relaxation during DCAP: a cyclic character of structure formation due to alternation high-rate processes of fragmentation and dynamic recrystallization, is changed by the processes of fragmentation and partial strain aging with the precipitation of second-phase nanosized particles. The temperature-time annealing (aging) conditions of Cu-Cr-Zr SMC alloys obtained by DCAP for improvement of mechanical properties and electrical conductivity was established. In particular, for the Cu-0.14Cr-0.04Zr SMC alloy, it has been shown that the optimal combination of microhardness (HV=1880 MPa), electrical conductivity (80% IACS) and strength (σ0.2=464 MPa, σu =542 MPa) at retaining satisfactory plasticity was obtained by treatment: DCAP+400°C, 1 h. The increased level of mechanical properties of alloys, compared to copper, is associated with additional strengthening due to precipitation of nanoparticles (5-10 nm) of the Cu5Zr and Cr during DCAP and aging. It has been shown that the low-alloyed Cu–Cr-Zr alloys possess a high ability to strengthen via the methods of DCAP and SPD by sliding friction. It has been determined based on the example of Cu–0.09Cr–0.08Zr alloy that the wear rate of samples with the SMC structure obtained by the DCAP method decreases by a factor of 1.4 compared to coarse-grained state. It was established that the combined treatment DCAP + 400°С + SPD by friction of the alloy gives rise to the friction-induced NC structure with grains 15– 60 nm in size in the surface-layer material, which provides a high level of the microhardness (3350 MPa) and satisfactory tribological properties.
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