Grain refinement kinetics and strengthening mechanisms in Cu–0.3Cr–0.5Zr alloy subjected to intense plastic deformation

Abstract

The ultrafine-grained microstructures, mechanical properties and electrical conductivity of a Cu-0.3%Cr-0.5%Zr alloy subjected to equal channel angular pressing (ECAP) at a temperature of 400°C to a total strain of 1, 2, and 4 were investigated. The ultrafine-grained microstructure resulting from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process is considered as a type of continuous dynamic recrystallization. The multiple ECAP process resulted in substantial strengthening of the alloy. The yield stress of CuCrZr alloy in the initial solution treated condition (ST) increased from 65 MPa to 476 MPa after four ECAP passes at 400°C. For the aged condition (AT), the yield stress increased from 170 MPa to 511 MPa after four passes. The strengthening was attributed to the grain refinement and high dislocation densities evolved via large strain deformation. Bacon-Kocks-Scattergood modification of the Orowan model is sufficient for acceptable description of the precipitation hardening of AT specimens during ECAP processing; this finding is in excellent agreement with the experimental data. The discrepancy between the experiment and model for ST specimens disappears after taking into consideration additional precipitating of the supersaturated solid solution during preheating and ECAP processing.

Dislocation versus grain boundary strengthening in SPD processed metals: Non-causal relation between grain size and strength of deformed polycrystals

“…The above analysis shows both the model for volume-averaged dislocation and grain boundary (GB) creation as well as experimental data show that in SPD processed materials there is a strong non-causal correlation between d and ig, such that strength will always show a strong positive correlation with d -1/2 even if GB strengthening is a minor strengthening effect. Also other works have shown a strong correlation between modelled GB strengthening and dislocation strengthening for deformed metals and alloys [7,18,26,27,28,29]. This non-causal effect can only be eliminated if a complete recovery treatment is performed, i.e.…”

Strength properties and structure of CuCrZr alloy subjected to low-temperature KOBO extrusion and heat treatment

“…CuCrZr alloys usually contain 0.5÷1.5 wt% Cr and 0.03÷0.3 wt% Zr; however, alloys with a chemical composition significantly exceeding the above range are also made, e.g., Cu0.3wt%Cr0.5wt%Zr [4]. "Classical" alloy contains 1.0 wt% chromium and 0.1 wt% zirconium and the remainder is copper.…”

“…The acceptable minimum functional hardness of CuCrZr alloy of 100 HV (UTS at room temperature above 300 MPa) makes it possible to achieve "optimum thermal conductivity," which the alloy acquires as a result of aging with hot isostatic pressing at temperatures as high as 550°C [15]. In contrast, an alloy intended for contact wires should have the following parameters: UTS greater than 530 MPa, electrical conductivity of 78% IACS (International Annealed Copper Standard), and good thermal stability [4].…”

“…The most popular SPD method, often used during deformation of CuCrZr alloy, is the Equal Channel Angular Process (ECAP). It makes it possible to drastically increase the strength properties of Cu-0.87wt%Cr-0.06wt%Zr alloy to the level of YS = 535 MPa [25], and Cu-0.3wt%Cr-0.5wt%Zr alloy to YS = 511 MPa [4], despite the content of alloying agents (Cr and Zr) deviating from the "classical" alloy.…”

Dynamic strain aging precipitation of Mg17Al12 in AZ80 magnesium alloy during multi-directional forging process

“…By contrast, the DSA process can be effectively controlled during the Sever Plastic Deformation (SPD) by constantly increasing accumulative strains. In recent years, the DSA behavior during SPD process has been widely studied [6][7][8][9][10][11][12]. Roven et.…”