Cu alloys are widely used in industrial applicationsbecause of their excellent properties such as high thermal and electricalconductivity, heat resistance, ablation resistance and high strength. Cu-Walloys are extensively used as sweat cooling, contact alloy, electrical contactand electronic packaging materials 1-8. Whas high density, melting point and hardness than that of Mo that eliminate theapplication of Cu-W alloy. Mo is a good candidate to be replaced with W andMo-Cu alloys are also easy to sinter and process than W-Cu alloy.
In the Mo-Cu system the heat of mixing is positive (+18kJ/mole) 9 there is a signi?cantdifference in melting points and lactic parameter of copper (TCu =1083 °C, aCu= 0.361 nm) and molybdenum (TMo = 2625 °C, aMo=0.314 nm) which the solid solubility of Mo in Cu is 0.5 wt.% at 1100 °C 10, 11.
In the other hands Mo-Cu alloys is immiscible in both solid and liquid statesand do not form any alloy using conventional equilibrium methods such ascasting or liquid metallurgy 12. The extension of solidsolubility beyond the equilibrium values could be achieved by non-equilibriummethods, such as rapid solidi?cation process, vapor deposition, laserprocessing, sputtering, ion beam mixing, and mechanical alloying (MA) ofelements. Among mentioned methods MA is a simple method due to its ability toincrease solid solubility at ambient temperature and this process could achievea larger solid solubility extension. Plastic deformation, fracture and coldwelding of particles, during MA of the powder mixture, leading to a continuousmicrostructure re?nement of particles and increasing specific surface area.
Stackingfaults, vacancy and dislocation arrays increased in the particles grain duringthe process of mechanical milling of the powder mixtures and the cold weldingbetween the different particles minimizes the diffusion distance between atomsand solubility of elements increased in the nanostructured particles 13, 14.Many researches have been focused on synthesis Mo-Cualloys with MA processes which result fine grain alloys with homogeneousmicrostructures and excellent properties 2, 14-19.In the fabrication of Mo-Cu alloys with MA process, starting materials areoften mixed together elementally in the ball milling system 16, 19, 20.Sun et. al synthesized novel core shell Cu-Mo nanoparticles via a simple ball-milling of MoO3-CuO mixtureand subsequent hydrogen reduction process 12. In some other worksMo-Cu fabricated with combustion reaction using Al as reducing agent 21. Magnesio-thermalreduction of MoO3-CuO mixture oxides was reported to be high caloricprocess which proceeds in combustion mode 11. In the case of usingreducing metals such as Al, Mg, Na or Ca, that is most of the time challengingtask to purify nanocrystalline powders from undesired byproducts.
The advantageof using graphite as reducing agent is that CO2 gas is the byproductthat are removed simultaneously during the reaction. Lubricating properties ofgraphite also prevents the particles from accumulating during milling and leadsto the formation of smaller particles. Previous studies have shown theformation of nanocrystalline metallic powders via mechano-chemical reduction ofNiO 22, V2O5 23, CuO 24, 25MoO3 26 with carbon and theeffect of milling processing on the reduction of metal oxides were reported. In this paper, nano-crystalline Mo-Cu alloy has beensynthesized via co-reduction of molybdenum trioxide (MoO3) andcopper oxide (CuO) with graphite using high energy planetary ball milling andsubsequent heat treatment