High strength and good electrical conductivity in Cu–Cr alloys processed by severe plastic deformation

Abstract

Ultrafine-grained (UFG) microstructures in Cu–Cr alloys were processed by high pressure torsion (HPT). The improved hardness was accompanied by a reduced electrical conductivity due to the large amount of grain boundaries. The effect of heat-treatment after HPT-processing on the hardness and the electrical conductivity was studied for different chromium contents (0.75, 9.85 and 27wt%). For low Cr concentration (0.75%) the electrical conductivity increased considerably above 250°C, however the hardness decreased concomitantly. At the same time, for high Cr content (9.85% and 27%) the hardness was only slightly reduced even at 500°C, while the electrical conductivity increased to a similar level as before HPT due to grain boundary relaxation and decomposition of Cu–Cr solid solution. Our study demonstrates the capability of SPD-processing and subsequent heat-treatment to achieve a combination of high strength and good electrical conductivity.