HIGH-TEMPERATURE BEHAVIOR OF PRECIOUS-METAL BASE COMPOSITES

The high thermodynamic stability and exceptional mechanical properties of intermetallic compounds based on platinum group metals (PGMs) make them potentially exploitable as structural materials for elevated tem perature service. In this study, the development of high-temperature s trength was evaluated for a selection of eutectic composites based on Ru-Al, Ir-Al, Ru-Nb, Ir-Nb, and Ru-Al-Ni using compression tests. All the alloys tested were characterized by high strength at extreme tempe ratures, none more so than an Ir84Nb16 alloy which had a proof stress in excess of 600 MPa at 1300 degrees C. In addition, several alloys sh owed significant compressional ductility at room temperature. Of parti cular interest is the synergy of soft constituent phases in evolving s trengths greater than that anticipated by simple rules of mixture. The potential of secondary phases to advance both strength and room-tempe rature ductility makes these composites worthy of further investigatio n.