Mechanical and Material Properties of Metal Matrix Composite Conducting Alloys

The contact resistance and wear behavior of conducting contact surfaces is a function of hardness, applied load and material constituents. This paper presents mechanical and material properties of conducting alloys fabricated as functionally graded metal matrix composites (MMCs); in particular copper/tungsten, copper/tungsten carbide, and bronze/tungsten-carbide. Tungsten and in particular tungsten-carbide reinforcing particles are attractive in this application for their high hardness and concomitant wear resistance. A brief overview of MMC production methods with accompanying tradeoffs is presented. Results of measured properties such as electrical resistivity, hardness, and density will be presented. Optical microscopy was used to measure the reinforcing particle distribution and volume fraction of constituents within the MMCs. The results of the microscopy analysis explain the property variations as a function of position within the casting. It was demonstrated that the rule of mixtures can be used to compute material properties as a function of particle volume fraction. Material properties of the MMCs are compared and contrasted with other conducting alloys. Significant improvement in hardness with relatively low reduction in base material conductivity was observed.