Strong deformation anisotropies of ω-precipitates and strengthening mechanisms in Ti-10V-2Fe-3Al alloy micropillars: Precipitates shearing vs precipitates disordering

Unlike the general belief that either dislocations cut or by-pass the ω-precipitates contributes to the high strength of Ti alloys, here we uncovered a new strengthening mechanism of lattice disordering of ω-precipitates by investigating the deformation behavior of body-centered-cubic (bcc) single crystalline Ti-10V-2Fe-3Al (Ti1023) alloy micropillars. This unique ω-precipitate disordering strengthening mechanism emerges in-between the precipitate cutting and by-passing mechanisms, because the dislocations pile-up stress reaches the ideal strength of ω-phase. The ω-precipitates with four variants manifest the strong deformation anisotropies, as verified by both the crystallographic orientation analysis and energy landscapes from the first principle calculations. The combination of precipitates cutting of ω1-variant and precipitates disordering of ω2/ω3/ω4-variants leads to the formation of precipitate-free channel in bcc (146)_β-oriented Ti1023 alloy micropillars. Due to the presence of ω-precipitates, the bcc Ti1023 alloy micropillars exhibit stable plastic flow, associated with weak-size dependent superior strength. These findings provide fundamental understanding of the deformation characteristic of precipitate-hardening alloys, and have important implications for the design of small-scale materials.