W-Cu composite has been in use for the production of ammunitions, electrode materials for electric discharge machining (EDM), electrical contacts, microelectronic packages, weight balancing in space crafts and in sport vehicles. W -brass composite is a cheaper and an alternative candidate material for the above applications due to its lower sintering temperatures and lower cost of brass than that of Cu. This research was conducted with the main objective of densification of W -brass up to or closer to the theoretical density in order to produce a novel material that could be an alternative to W -Cu composites. The study revealed that conventional solid state and liquid phase sintering cannot be used for the densification of W -brass composhes due to mutual
insolubility between W, Cu and Zn, compact expansion, dezincification and poor wettability of W by liquid brass. The problem of poor densification was solved by mechanical alloying, direct infiltration and infiltration by shell-on-core. The powders were compacted into I Omm diameter and 3 to 4mm height green compacts. These green compacts were sintered at the temperature of 800 °C, 920 °C, 1000 °C 1 150 °C under pure hydrogen atmosphere for 1 - 2 hours. Both pre-mixed and pre-alloyed compacts were subjected to different heating and cooling rates. The mechanical alloying was carried out for 4, 5, 8, 10, 12, 13 and 15 h for the pre-mixed and pre-alloyed powders under pure argon atmosphere. The sintered compacts were tested for density, hardness, tensile strength, wear resistance, corrosion resistance, electrical conductivity and coefficient of thermal expansion. These processes of direct infiltration, infiltration by shell-on-core and mechanical alloying resulted in higher sintered density of up to 99% TD. The hardness of this composite increase as the weight fraction ofW increases. High hardness values ranging from 119-234 Hv were obtained compared to 154-182 Hv obtained in W-Cu of the same composition. A very low wear rate in the range of0.002-0.01 mm3/m was obtained. The tensile strength of the composite is within 89-130 MPa. After 35 days immersion in sea water, the corrosion rate of 0.81-0.52 mm/yr was obtained in the as received samples while the samples containing Fe activator had better corrosion resistance (0.10-0.11 mm/yr). The CTE values are within 7.40-13.89 x l0"6fC while that of W-Cu used in electronic packages ranges from 6.5-8.5 x J0"6fC. The
electrical conductivity of 18.45-27.37% lACS was obtained, compared to 26.77% lACS which is the national standard for W-Cu composite with 47 wt.% W. It was discovered that the addition of an activator deteriorates the electrical conductivity of this composite. In conclusion, W -brass composite with high density closer to the theoretical density, good mechanicaJ properties, corrosion resistance and physical properties was produced.
