Production of metal matrix composites (MMCS) by P/M method from direct recycled powders and investigation of mechanical properties of MMCS

In conventional recycling method, metal chips are casted after pressing and melting in electric arc furnace. Material loss occurs during the recycling from liquid metal due to the several reasons. Direct recycling method which produces the aluminium powder from aluminium chips using mechanical mill can be an alternative to conventional recycling method. Thus material and energy losses, and labour cost will be reduced by direct recycling method without melting. In this study, 7075 aluminum alloy powders produced by disc mill from metal chips and mechanical properties of P/M and reinforced %10 SiC composites produced by direct recycling method from these powders are investigated. Milling parameters are 1000, 1200, 1400, 1500 rpm milling speeds and 2, 4, 6, 8, 10, 12 min milling times. The chips are obtained with commercial coolant, mixture of paraffin ethanol and canola oil. With XRD and XPS analysis, paraffin influence of aluminum oxide layer on powder surface was investigated. Density, hardness and rupture strength of composites was determined. With SEM analysis, influence of microstructure on mechanical properties was investigated. As a result, 7075 Al alloy powder produced by the mechanical milling method are flat and irregularly shaped. By delimitation of oxide layer on aluminum powder surface composites can be produced with high strength and hardness. Paraffin limits the oxides on aluminum alloy powder. Achieving optimum powder size increases strength and hardness. Powders should be in size of sufficient contact with each other on high pressure and fine grained not as agglomerating. Density of composites manufactured from paraffin powder is relatively low. Paraffin has a negative effect on density, strength and hardness of composites.