Phase Stability of Al3X Alloys (X = Ti, Zr, Hf)

Abstract

Current research on ordered intermetallics is motivated by the need of high-strength structural materials for high-temperature applications. Single-phase early transition metal aluminides A13X (X = Sc, Ti, V, Y, Zr, Nb) have desirable properties such as high melting temperature, low density, good oxidation resistance, and low chemical interdiffusion (i.e., good thermal stability). These properties make them suitable for potential structural applications at high temperatures (in single-phase form) or at intermediate temperatures (as a strenthening phase in two-phase aluminum alloys). Single-phase A13X alloys are brittle and this has prevented any serious consideration for applications. However, two-phase Al-Al3X alloys have the potential for developing “alumalloy” [1], which has a low coarsening rate because of small lattice mismatch with the aluminum matrix, and are useful to about 420° C. The electronics industry is increasingly interested in thin-film trialuminides for applications in which diffusion barriers are needed to decrease the electromigration of the interconnecting electrode and to suppress hillock formation [2].