An ultrasound-based evaluation of cubic symmetry preservation and homogeneity in elastic behavior of fl plus w and fl plus a Ti-alloys

Elastic constants of dual-phase fl-titanium alloys with different phase compositions and different volume fractions of individual phases were investigated using resonant ultrasound spectroscopy and transient grating spectroscopy. It was shown that even for high volume fractions of the secondary phases (w and a), the crystals can retain cubic symmetry and homogeneity in their elastic behavior, both at the macro-scale and at the micro-scale, unless the secondary phases precipitate under external stress violating this symmetry. In contrast, a material heat-treated under uniaxial compression deviates from cubic symmetry in its macroscopic behavior, and its micro-scale elastic behavior is heterogeneous. The results also reveal that the w and a particles have different impacts on the elastic constants of the fl-matrix, the former affecting only the shear part of the elastic response, while the latter also the bulk modulus.