A Trade–off between Mechanical Strength and Conductivity in Oxide Dispersion–Strengthened–Cu Alloys Fabricated by Mechanical Alloying

Abstract

A trade–off between mechanical strength and thermal conductivity prevents the achievement of higher thermal conductivity in copper alloys, while maintaining the high mechanical strength of copper at high temperatures, which can result in energy savings and a lower carbon footprint. Oxide dispersion–strengthened (ODS) Cu–xY₂O₃ (x=0, 0.5, 1, 2 wt%) alloys were prepared by mechanical alloying (MA) using a water–cooled high–energy ball milling machine and then sintered with a hot press. The indentation hardness of the sintered materials increased with the amount of Y₂O₃. Microstructural observations revealed that high strengths for the Cu– Y₂O₃ ODS alloys was achieved by both oxide dispersion and fine grains. However, the thermal diffusivity was not simply dependent on the amount of Y₂O₃, which was higher in both Cu–0Y₂O₃ and Cu–1Y₂O₃ but lower in the others. Among the factors affecting the thermal diffusivity, the amount of impurities, such as Fe and Cr, introduced during the MA process are responsible for the higher values of thermal diffusivity in Cu–0Y₂O₃ and Cu–1Y₂O₃. The obtained results indicate that ODS–Cu alloys fabricated by MA and sintering can overcome the trade–off between mechanical strength and thermal conductivity when the solute impurities are suppressed.