Stress release-induced interfacial twin boundary ω phase formation in a β type Ti-based single crystal displaying stress-induced α” martensitic transformation

Y. Yang (1) , P. Castany (1) , E. Bertrand (2) , M. Cornen (1) , J.X. Lin (3, 4) , T. Gloriant (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 IMN - Institut des Matériaux Jean Rouxel
3 CAS - Chinese Academy of Sciences [Beijing]
4 Fujian Institute of Research on the structure of Matter

The ω phase transformation in numerous group IV transition metals plays a key role to change the phase stability and modify mechanical properties, although its formation mechanisms and effect to accommodate strains are still unclear. A <1 1 0>β single crystal of β-type Ti-24Nb-4Zr-8Sn alloy (wt. %) is used to investigate the aforementioned problems. This alloy displays a β to α” stress-induced martensitic transformation, which is reversible and leads to superelasticity. Profiles obtained from in situ synchrotron X-ray diffraction during cyclic tensile tests reveal definitely the appearance of ω phase due to applied stress releasing after unloading while these identified ω peaks shall vanish totally on subsequent loading. TEM microstructural observations show its morphology as thin layer locating on the boundary of {1 1 2}<1 1 1>β twins coinciding well with the feature of interfacial twin boundary (ITB) ω phase, which is proved to be formed passively during the reversion of {1 1 0}<1 1 0>α” twins. The martensitic twinning components of {1 1 0}<1 1 0>α” are indeed confirmed from crystallographic reconstructions based on the orientation relationship between the β and α” phases. A geometrical model is hence schematically used to analyze in details the orientation relationships between both deformation {1 1 2}<1 1 1>β twins and ITB-ω phase, as well as with the original {1 1 0}<1 1 0>α” twinning.

Keywords: Interfacial phase; ITB-ω phase; Stress-induced martensitic transformation; {1 1 2}<1 1 1> β; Deformation twinning; {1 1 0}<1 1 0>α”

Domains: Engineering Sciences [physics]; Mechanics [physics.med-ph]; Mechanics of materials [physics.class-ph]

Y. Yang, P. Castany, E. Bertrand, M. Cornen, J.X. Lin, et al.. Stress release-induced interfacial twin boundary ω phase formation in a β type Ti-based single crystal displaying stress-induced α” martensitic transformation. Acta Materialia, 2018, 149, pp.97-107. ⟨10.1016/j.actamat.2018.02.036⟩. ⟨hal-01740146⟩