Strength and Toughness of Single-Phase and Dual-Phase High-Temperature Intermetallics

Abstract

AbstractThe strength and toughness of several high-temperature beryllium-niobium (Be12Nb and Be17Nb2) and iridium-niobium (lr3Nb) intermetallic compounds have been evaluated. Materials were prepared by high-rate sputter deposition and characterized by x-ray diffraction and analytical electron microscopy before and after heat treatment. As-sputtered microstructures were varied from amorphous to microcrystalline by control of substrate temperature. Grain size, degree of order, and second-phase distribution were modified by subsequent heat treatment. Strength as a function of temperature was assessed by hot hardness tests and toughness estimated from indentation-induced crack lengths. Intermetallics exhibited very high strength and low toughness up to temperatures of ˜1000 C. Mechanical behavior was a direct function of the microstructural parameters including matrix phase composition, second phase distribution, and degree of order.