Mechanical behaviors of Ti-V-(Al, Sn) alloys with α′ martensite microstructure

The mechanical properties and deformation behavior of Ti-V-(Al, Sn) alloys with a α′ martensite microstructure are examined in this work. In as-quenched Ti-V-Al alloys consisting of α′ martensite microstructure with compositions near α - (α + β), the cold-rolling ability drastically decreases from a reduction of more than 75% to less than 40% with an increase in Al content. While, excellent cold-rolling ability (more than 75% reduction) is seen in the constituent phases of α′ in the compositional region near β - (α + β), and α″ and β. On the other hand, in as-quenched Ti-V-Sn alloys, excellent cold-rolling ability with a reduction of more than 80% that is independent of phase constituents is seen. In α′ martensite Ti-V-Al-Sn alloy with compositions in α - (α + β) that is tensile-deformed at a strain of 5%, a homogenous deformation substructure with straight dislocations is seen in alloy that with a low Al content. In contrast, the dislocation substructure begins to exhibit a planar configuration with increasing Al content. This change in deformation substructure due to increasing Al content is considered to cause the low ductility in α′ martensite Ti alloy that contains high Al. On the other hand, in α′ martensite Ti-V-Al alloy with a composition near β - (α + β), plastic deformation is found to be proceeded via the activation of the basal 〈a〉 slip and the {101̄1} twin with a homogenous deformation substructure. As a consequence, this deformation mode is considered to cause the high ductility in the α′ phase as compared with the equilibrium (α + β) phase.