Effect of strain on microstructural development during uniaxial compression of metastable beta Ti–10V–2Fe–3Al alloy

The effect of strain during uniaxial compression on mechanical behavior of Ti–10V–2Fe–3Al alloy produced by blended elemental powder metallurgy and containing a metastable β matrix with ~0.1 fraction of α phase was investigated. A detailed scanning transmission electron microscopy study revealed the initiation of slip and deformation-induced α′′ martensite and ω_D formation at the beginning of plastic deformation in the stress plateau region of stress-strain curve. {332}<113> twinning occurred at a later stage. Deformation-induced ω_D formed in the β matrix and within {332}<113> twins, but was consumed by other deformation products at strains exceeding 0.2. Formation of {112}<111> twins within {332}<113> twins and along their interfaces with the matrix was uncovered. The rate of development of deformation products among the β phase grains was non-uniform with many being fully transformed to α′′ martensite by 0.4 strain, whereas others experienced deformation conditions related to stress plateau region (<0.1 strain) and were only partially transformed. Formation of deformation-induced nanoscale ω_D at the α′′ martensite/β interface was found only in the sample with more stable β matrix due to 0.26 fraction of α being present. This was related to a higher rigidity of the β phase resulting from the higher levels of alloying elements. This induced the triggering of β→ω transformation by stresses arising from α′′ martensite formation.