Aluminum superalloys for use in high temperature applications

Abstract

Aluminum-zirconium and aluminum-zirconium-lanthanide superalloys are described that can be used in high temperature, high stress and a variety of other applications. The lanthanide is preferably holmium, erbium, thulium or ytterbium, most preferably erbium. Also, methods of making the aforementioned alloys are disclosed. The superalloys, which have commercially-suitable hardness at temperatures above about 220° C., include nanoscale AlZr precipitates and optionally nanoscale AlEr precipitates and nanoscale Al(Zr,Er) precipitates that create a high-strength alloy capable of withstanding intense heat conditions. These nanoscale precipitates have a L1-structure in α-Al(f.c.c.) matrix, an average diameter of less than about 20 nanometers ('nm'), preferably less than about 10 nm, and more preferably about 4-6 nm and a high number density, which for example, is larger than about 10m, of the nanoscale precipitates. The formation of the high number density of nanoscale precipitates is thought to be due to the addition of inoculant, such as a Group 3A, 4A, and 5A metal or metalloid. Additionally, methods for increasing the diffusivity of Zr in Al are disclosed.