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In this paper, (TiC+TiB2)/Cu composites are successfully prepared by mixing and hot-press sintering of Cu powder with mechanical alloyed Ti-B4C powder mixture. Results show that, mechanical alloying can ensure the decomposition and solution of B4C in to Ti powder, and thus form a solution of ternary Ti-C-B system. As a result, on-set temperature of Ti-B4C in-situ reaction is decreased and reaction products are TiC+TiB2, because that the formation of TiB2 has lower Gibbs free energy change than that of TiB. When the content is low, reinforcements presents to be small and well-dispersed particles in Cu matrix, and the reinforcements and matrix is well combined, resulting in significant improvements on hardness of composites. With the content increases, reinforcements aggregate seriously, and the interface transfers to be simple mechamical package. When the designed content of reinforcements is 15vol.%, the electrical conductivity of prepared (TiC+TiB2)/Cu composites is 47.1%IACS, much higher than composites prepared from non-milled Cu-Ti-B4C mixture (12.46%IACS), suggesting that mechanical alloying can accelerate reaction between Ti-B4C while prevent solution of Ti into Cu matrix.