Revisiting deformation anisotropy of ω-variants via microcompression of <110>β oriented Ti85Nb15 alloy

The disperse-precipitated ω has a significant strengthening effect on metastable β-titanium (Ti) alloys. The (211)β[1¯11]β/(2¯11)β[111]β slip systems are massively activated during plastic deformation. However, the interaction of the four-equivalent crystallographic ω variants with these slip systems has not been investigated. Here, we revisit the evolvement of the internal ω-precipitate via systematically exploring the compressive mechanical behavior of <110>β-oriented Ti85Nb15 micropillars. Firstly, the four ω-variants show the strong deformation anisotropies. Secondly, this deformation anisotropy is pertinent to the interaction with dislocations. Dislocations originating from the β-matrix can continuously across the ω1-variant, but have no ability to across the ω2 variant. The accumulation of dislocations in the interface of ω2/β leads to severe local stress concentrations that ultimately prompts the dismemberment of ω2. Finally, we confirmed by first-principles calculations that the proliferation of ω1-variant owing to the reorientation of ω2-variant, that is, ω2→ω1, rather than a dissolution-reprecipitation mechanism, ω2→β→ω1. These findings are beneficial for a comprehensive understanding of the deformation mechanism of the ω-variants in metastable β-Ti alloys.