Fabrication of metal matrix composites by squeeze cast technique

The need for new engineering materials with the advancement of modern technology had led to the development and use of new materials. Metal matrix composites are candidate materials to meet the necessity with their superior properties. Because of this, improving the properties and processing methods of metal matrix composites have been the subject of much attention for materials engineering. In this study, composite of an Al?7%Si?0.7%Mg based matrix alloy reinforced with 20 vol.% of electroless nickel coated SiC particles with an average size of 15?m was produced by squeeze casting technique. In addition, SiC substrate and particles were coated by oxidation, sol-gel and electroless nickel coating methods to obtain a SiO2, TiO2 and Ni coating, respectively. Also, an investigation has been carried out on the effect of doping TiO2 with Cu, Fe or Ni on the wettability. A considerable improvement in wettability has been observed with Ni coated SiC substrates compared to SiO2 and TiO2 coatings. However, wettability results indicate that while doping TiO2 with Fe has not an effect, Cu and Ni reduce the wettability. The microstructural, interfacial and mechanical properties of the produced composite have been investigated. The evaluation of microstructure show that, SiC particle distribution is homogenous in general and the matrix phase exhibit a pore-free and dentritic structure. Interfacial examinations indicate that electroless nickel coating has not degraded during the fabrication process and prevent the formation of Al4C3. Ultimate tensile strength, yield strength and elongation of the produced composite was found to be 161 MPa, 133 MPa and 2,34% respectively. Also, fractography observations demonstrate that the failure occurred as a ductile fracture of the matrix alloy and brittle fracture of SiC particles.