Stress-Induced α″ Martensitic Transformation Mechanism in Deformation Twinning of Metastable β-Type Ti-27Nb-0.5Ge Alloy under Tension

Abstract

In this study, the formation mechanism of the stress-induced α″ martensitic phase in the deformation twinning (DT) band of metastable β-type Ti-27Nb-0.5Ge (at.%) alloy under tension was investigated. A preferential nucleation site for the stress-induced α″ martensitic transformation is inside a DT band with high dislocation density. The α″ martensitic phase developed in the DT band with increasing applied plastic strain. The α″ martensitic phase subsequently grew to intersect other DT bands, forming secondary DT bands themselves in the parent β grains.

Fig. 3 SEM images of (a) region 3 in Fig. 2 and (b) TEM sample via FIB cutting. (b) The bright-field TEM image of the α″ martensite and DT formed on the β matrix. The SADPs of the (d) α″₁, (e) DT, and (f) α″₂ regions marked by the white circles in (c). (g) A schematic image representing the SADPs consisted of the β, α″, ω₁, and ω₂ phases having the specific orientation relationships.