Coarsening phenomenon of L12 precipitates in rapidly solidified Al-3at%(Ti, V, Zr) system

It is of interest how to design the Al-Ti-V-Zr system and optimize the compositions of added transition elements to minimize the lattice misfit, and thus an interfacial energy, and maximize the coarsening resistance and, at the same time, optimize the volume fraction of the precipitated stable D023 Al3M phase. These all can be beneficial to the high temperature strength. The coarsening kinetics of the L12 precipitate in the present study were very slow. Furthermore, the transformation of the L12 phase to the D023 phase was not observed. The free energy change for the L12-D023 transformation was probably reduced due to the reduction in lattice misfit and strain. In the previous works, the authors designed alloys assuming the stable DO23 phase would play an active role in the aging condition, but this prediction was not observed. Instead, L12 precipitates were dominant. Owing to the low coarsening rate and these high thermal stability of the precipitated phases, Al-Ti-V-Zr systems show promise as bases for high-temperature high-strength Al alloys