Change of elastic behavior in binary β-type Ti alloys with deformation

The aim of this study is to systematically investigate the elastic behavior with deformation of the binary titanium alloys of Ti-Mo, Ti-Nb and Ti-V. The stress-strain curve using cyclic load-unloading tensile test of alloys composed of α″ martensite, e.g. 20Nb and 8Mo, showed the peculiar pseudo-elastic behavior. A little higher content of β-stabilizer alloys of 38Nb, 10-14Mo and 15-20V, which were composed of β and commensurate ω phases by quench, indicated the liner elasticity until the yield but changed to the extreme pseudo-elasticity after {332}〈113〉 twin formation. Dynamic observation made clear certain {332}〈113〉 twin initially formed on tensile loading disappeared during unloading process. Medium content of β-stabilizer alloys of 42Nb and 16Mo exhibited a concave downward elastic curve and were deformed by mixture mode of slip and {332}〈113〉 twin. On the higher content alloys it was found that the stress level on which Young's modulus begins a rise increases with the increase of alloy content. These elastic features were summarized as change of apparent Young's modulus with increase of strain.