| In recent years, national electric multiple units (EMU), electrified high-speed rail and other new electrified railway construction has entered a stage of rapid development. At the same time, as one of core components supporting the driving force, the contact wire is also facing new opportunities and challenges, requiring higher tensile strength (≥550MPa), better conductivity (≥80%IACS), better resistance to softening (≥500℃) and friction properties. As a new type of plastic processing methods, the technology of equal channel angular pressing (ECAP) can make sample to obtain severe plastic deformation, in the case of not changing the material size. It is very effective in grain refinement, tissue-distribution improvement, and ultimately improves material strength, toughness and other macroscopic properties.This paper uses Cu-0.5Cr-0.16Zr alloy for the study, choose large deformation technology of ECAP combined with heat treatment, study effects of different ECAP extrusion passes, different aging temperature and time on the tensile strength of alloys, micro-hardness, relative conductivity and softening temperature, from which to explore optimal deformation-heat treatment'process of preparing high strength and high conductivity Cu-Cr-Zr alloy. At the same time, the use of optical microscope, scanning electron microscopy, X-ray diffraction and EDS spectrometer observes changes in alloy microstructure during the process of ECAP deformation and Aging precipitation, and also determine the type of precipitates and tensile fracture mechanism. Finally, the paper detailed analyzes Cu-Cr-Zr alloy'strengthening mechanisms, conduction mechanism, anti-softening mechanism, and the role of ECAP technique in these ones.After eight passes ECAP deformation in Be way, Cu-Cr-Zr alloy successfully obtains organization of ultra-fine grain, tensile strength 672MPa, micro-hardness 186HV, and relative conductivity 27.4% IACS. Then deformed alloy ages at different temperatures, time, and best summed up deformation-heat treatment' process (6 passes ECAP+450℃/1h aging), when strength, hardness and conductivity are significantly increased, respectively,903MPa,280HV. and 73.6% IACS, so mechanical properties and electrical properties form a good match. Meanwhile, the softening temperature is from 460℃of 0 pass up to 580℃of 6 passes, and effectively improve the softening resistance of Cu-Cr-Zr alloy.With the increase of ECAP extrusion pass, the tensile specimen changes from typical ductile fracture to brittle fracture along the grain; aging precipitates are small, dispersed like, and composed mainly of elemental Cr and Zr-rich phase.By ECAP and subsequent heat treatment. Cu-0.5Cr-0.16Zr alloy'mechanical and electrical properties have been significantly increased, which is because:ECAP not only can produce hardening effects, and also can effectively refine grain, to fine-grain strengthening; on the other hand, after processing by ECAP. dislocations, subgrain boundaries and other micro-defect density increases significantly, making proliferation channels and nuclear position Correspondingly increase, which is very helpful for the Cr/Zr hard phase' precipitation. Therefore the second phase in the subsequent heat treatment is sufficiently precipitated in a very short period of time, and the second-phase particles present Small equiaxed state homogeneously distributed in the copper matrix around. Alloy microstructure changes in the final bring a variety of macroscopic properties of Cu-Cr-Zr alloy significantly improved. |
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