Formation of {332}<113>β twins from parent {130}<310>α″ plastic twins in a full α″ Ti-Nb alloy by annealing

Highlights: • The solution-treated, deformed and annealed structures of a full α″ martensitic Ti-23Nb (at.%) alloy have been investigated. • The self-accommodated feature of the α″ martensites is presented by EBSD. • The martensites transform into β phase after annealing and the β phase is retained to room temperature by furnace-cooling. • Direct evidence is given for the formation of {332}_β twins from {130}_α″ plastic twins by ex-situ EBSD observations. • A possible {351}<1$\overline{1}$2>_α″ twinning in α″ phase that corresponds to {332}<11$\overline{3}$>_β is proposed. - Abstract: The solution-treated (ST), deformed and subsequently annealed microstructures of a full α″ martensitic Ti-23Nb at.% alloy have been investigated by optical micrograph (OM), X-ray diffraction (XRD) and electron back-scattered diffraction (EBSD). The results show that both the self-accommodated α″ martensites in ST sample and re-orientated martensitic structure and plastic {130}_α″ twins in the Deformed sample fully transformed into the β phase with a small amount of the ω phase by annealing. The ex-situ EBSD measurements showed that the {332}_β twins occur in the Annealed sample, which correspond to the {130}_α″ plastic twins of the α″ phase in the Deformed sample, and thus give a direct evidence that the {332}_β twins in the β phase form from the reverse martensitic transformation of the {130}_α″ plastic twins in the α″ phase. Moreover, it's also expected from EBSD results that in addition to $\left\{130\right\}<3\overline{1}0>$_α″, the possible <$\left\{351\right\}<1\overline{1}2>$_α″ twinning system of the α″ phase corresponds to the $\left\{332\right\}<11\overline{3}>$_β twinning of the β phase.