A correction to optimum alloy composition for design of high-temperature high-strength Al [sbnd]Ti [sbnd]V [sbnd]Zr alloys through thermodynamic calculations

Abstract

It is very likely that high-strength Al-base alloys up to 698K can be developed 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. According to a review paper by Adam, several Al-base systems containing transition metal elements for potential elevated temperature use were suggested based on low values of diffusivities and solubilities. 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 DO{sub 23}-type Al{sub 3}Zr compound, creating Al{sub 3}(Ti,Zr) and Al{sub 3}(V,Zr), respectively. It was of interest to design the Al-Ti-V-Zr system and optimize the compositions of added transition elements to minimize the lattice mismatch, and thus an interfacial energy, and maximize the strengthening effects at high temperatures. The authors were able to do experiments on phase stabilities of Al{sub 3}Ti-Al{sub 3}V-Al{sub 3}Zr system and revise the thermodynamic parameters of this system. Therefore, this study reports onmore » the new optimum alloy composition which is supposed to maximize the coarsening resistance of the strengthening Al{sub 3}(Ti,V,Zr) phase at high temperatures of service in this system.« less