Metastable β-titanium alloys exhibit good cold formability due to a body-centered cubic crystal structure. However, since the primary plastic deformation mechanism also changes with the amount of β-stabilizing element, their mechanical properties have not been fully understood especially under biaxial loading conditions. In this study, the uniaxial and the biaxial compression tests were conducted on binary metastable titanium-molybdenum (Ti-Mo) alloys with Mo content from 10 to 18 mass% and the effect of Mo content on compressive plastic deformation behavior was investigated. The clear β-stabilizer content dependency was found on the stress-strain relations. The electron microscopy revealed that the {332} twin was activated on Ti-10~16Mo alloys. Meanwhile, Ti-18Mo alloy exhibited higher yield stress and lower strain hardening rate. It was also found that the area fraction of twins in biaxial compression was lower than that in uniaxial compression. Based on those results, the mechanism that induced changes of plastic deformation behavior with Mo contents in uniaxial and biaxial compressions was discussed with relation to the activation of deformation twinning.
