**5.5 Production of metal matrix composites**

Use of the countergravity casting technique is gradually branching into novel materials production. An emerging field of application is the production cast Metal Matrix Composites (MMC) which can be cast into complex, intricate geometries. These materials have found applications in diverse fields, from high quality reflective mirrors to optical and laser equipment (O'Fallon Casting, 2009). There has been increased interest in the use of cast aluminium/silicon carbide MMC for optoelectronics packaging due to its compatible coefficient of thermal expansion, high thermal conductivity, and potential to produce parts at low cost (Berenberg, 2003). In ring laser gyros, these MMCs are displacing traditional favourites like beryllium and stainless steel in the production of dimensionally stable mirrors that can withstand extreme thermal cycling (Mohn and Vukobratovich, 1988).
