Estudo de um compósito Mo-Cu obtido pela redução de pós de heptamolibdato de amônia e cobre moídos e sinterizados com fase líquida

Abstract

The composite Mo-Cu combines the high electrical and thermal conductivity of copper with the wear resistance of molybdenum. The many applications of this system are in electrical contact devices and heat sinks. The formation of this composite with low density compromises performance in the applications of this material. In addition, the mutual insolubility between copper and molybdenum makes it difficult to obtain this material the same or near density of theoretical density. However, the Powder metallurgy (PM) technique, through the steps of high energy milling (HEM), conformation/compacting and sintering with liquid phase, it’s ponted out as viable route to obtain this composite. High energy milling produces composites powders with high phase homogeneity and small particle size, which induces na increase in the sinterability of immiscible systems as well as the Mo-Cu system. Therefore, this work investigated the influence of reduction temperature of the composite powders HMA-15,34%Cu prepared by high energy milling, as well as the effect of this preparation on the densification, microstructure and properties of the sintered compacts Mo-25%Cu. Powders HMA-15,34%pCu were prepared for mechanical mixing and high energy milling. The milling was done in planetary mill Pulverisset 7 with container and balls of hard metal under atmosphere of ethyl alcohol and at 400 rpm for 20 h. The mass ratio of powder to ball was 1:5. Such powders were reduced to 700 °C, 750 °C and 800 °C in a tubular oven under flow of hydrogen (H2) of 316 ml/min. The Mo-25%Cu powders obtained were pressed at 250 Mpa in a uniaxial cylindrical matrix and green compacts produced were sintered at 1150 °C for 1 h under H2 atmosphere. Sintered compacts of Mo-25%Cu powders milling and reduced to 700 °C reached 94.1% of theoretical density. However, an electrical condutivity of 39,7 IACS and a Vickers microhardness of 341,63 Hv were obtained by the compacts sintered Mo-25%Cu powders milling and reduced to 750 °C.