Abstract
Multi-pass equal-channel angular pressing (EACP) was applied to produce ultrafine-grained (UFG) Cu-0.2wt%Mg alloy contact wire with high mechanical/electric performance, aim to overcome the catenary barrier of high-speed trains by maximizing the tension and improving the power delivery. Microstructure evolution and overall properties of the Cu-Mg alloy after different severe-plastic-deformation (SPD) routes were investigated by microscopic observation, tensile and electric tests. The results show that the Cu-Mg alloy after multi-pass ECAP at 473 K obtains ultrafine grains, higher strength and desired conductivity. More passes of ECAP leads to finer grains and higher strength, but increasing ECAP temperature significantly lower the strength increment of the UFG alloy. Grain refinement via continuous SPD processing can endow the Cu-Mg alloy superior strength and good conductivity characteristics, which are advantageous to high-speed electrification railway systems.
Highlights
With the rapid development of high-speed electric railway, mainly, advanced metallic materials used for contact wire are desired
Copper alloy are usually required to possess high tensile strength and good conductivity, with the aim to overcome the catenary barrier of high-speed trains by maximizing the tension and improving the power delivery
It is important to note that some abnormal methods have been reported to achieve a good combination of strength and conductivity [1,2], but those methods are relatively complicated in commercial applications
Summary
With the rapid development of high-speed electric railway, mainly, advanced metallic materials used for contact wire are desired. Most of the reports were focused on adding small amounts of alloy elements (such as Cr, Ag, Zr, Nb, Co, etc.) to pure copper [3,4,5,6] or applying hardening processes (such as drawing or rolling) [6] Those conventional strengthening methods induce various kinds of defects (dislocations, reinforcing phases, point defects, grain boundaries), raising electrical resistivity of Cu alloy because of the scattering of conducting electrons [7,8]. A novel severe-plastic deformation (SPD) procedure, namely equal-channel angular pressing (ECAP), has been applied for obtaining ultrafine-grained (UFG) copper alloy with high strength, large ductility, and good electrical conductivity [10,11,12]. ECAP at 473 K for (b) 1 pass, (c) 4 passes and (d) 16 passes
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