Orientation-dependent deformation behaviors of β single crystal micropillars in a metastable β titanium alloy

The compressive deformation behaviors were investigated in metastable β Ti–7Mo–3Al–3Cr–3Nb alloy single crystal micropillars oriented to [011]_β and [001]_β. The study demonstrates that the metastable β titanium single crystal oriented to [001]_β exhibits nonlinear elastic behavior with hysteresis, which is attributed to reverse β to α″ transformation. Furthermore, the yield strength of the single crystal oriented to [011]_β is almost twice as of the single crystal oriented to [001]_β, which is influenced by the different roles of ω_ath in both pillars due to differences in shear modulus G, in addition to being determined by the deformation mechanism at yielding. The continuous impedance to dislocation motion of ω and α″ phase in the pillar oriented to [011]_β leads to a stable plastic flow behavior, but reverse β to ω phase transformation facilitating the formation of massive SIMα″ results in a sudden strain burst in the pillar oriented to [001]_β. Finally, we find that the pillar oriented to [011]_β is dominated by dislocation slip but SIMα″ occupies a dominant position in the pillar oriented to [001]_β in the early deformation stage, which is same as predicted based on the martensitic transformation theory in metastable β titanium alloys.