HIGH-TEMPERATURE EVALUATION OF TOPOLOGICALLY CLOSE PACKED INTERMETALLICS

This report summarizes the high temperature mechanical properties evaluation, oxidation resistance and ternary alloying studies conducted on a category of compounds referred to as the topologically close packed (TCP) structures. Those compounds evaluated to the greatest extent were Cr2Nb, Co2Nb and Nb2Al, while Fe2Nb, Fe2Zr, Co2Zr, Cr2Hf, Mo2Hf and W2Hf were investigated to a lesser degree. The zirconium containing compounds resulted in pyrophoric powders thus limiting their utility. Elevated temperature bend, creep and cyclic oxidation tests were conducted on a number of these compounds to establish baseline properties. Ductile-brittle transition temperatures are reported as well as ultimate strengths at temperature, minimum creep rates and creep activation energies, and oxidation rates and oxide products.