Design of high-temperature high-strength AlTiVZr alloys

Abstract

This paper reports that it seems plausible to develop high-strength Al-base alloys useful up to 698K in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. An additional factor to be considered is the stability of the hardening phase with respect to Ostwald ripening. This coarsening resistance is necessary so that the required strength level can be maintained after the long-time service at high temperatures. The equilibrium crystal structures of Al{sub 3}Ti, Al{sub 3}V and Al{sub 3}Zr are tetragonal D0{sub 22}, D0{sub 22} and D0{sub 23}, respectively. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al{sub 3}(Ti, V). Much of titanium and vanadium can be substituted for zirconium in the D0{sub 23}- type Al{sub 3}Zr compound, creating Al{sub 3}(Ti, Zr) and Al{sub 3}(V, Zr), respectively. In particular, it has been reported that fcc L1{sub 2}-structured Al{sub 3}M dispersoids form in the rapidly solidified Al-V-Zr and Al-Ti-Zr systems and both L1{sub 2}more » and D0{sub 23}-structured Al{sub 3}M phases showed slow coarsening kinetics.« less