Effects of milling time on hardness and electrical conductivity of in situ Cu–NbC composite produced by mechanical alloying

High-energy ball milling was used to synthesis in situ a copper-based composite. Cu, Nb and graphite powder mixture were mechanically alloyed in a planetary ball mill for various milling times (2, 8, 16 and 32 h), in an argon atmosphere. The nominal composition was Cu–11.77%Nb–1.52%C, which corresponded to Cu–15 vol.% NbC. XRD analysis showed that NbC particle was precipitated in the Cu–Nb–C after the sintering process. This particle had improved hardness of the in situ composite. This is attributed to the crystalline refinement and lattice strain of NbC due to the mechanical alloying. Low value of electrical conductivity was obtained in in situ composite as a result of electron scattering by fine NbC particle and copper grain. The results had shown that by increasing milling time both in situ and ex situ properties Cu–NbC composites were changed.