A new beta titanium alloy system reinforced with superlattice intermetallic precipitates

Knowles, Alexander J.; Jun, Tea Sung; Bhowmik, Ayan; Jones, Nicholas G.; Britton, T. Ben; Giuliani, Finn; Stone, Howard J.; Dye, David

Scripta Materialia 140 (2017)

Titanium alloys traditionally lack a nm-scale intermetallic precipitate that can be exploited for age-hardening from solid solution. Here such a strengthening concept is developed in the Ti-Fe-Mo system, with it being found that a high temperature β (bcc A2) single-phase field for homogenisation can be obtained, which following ageing (750 °C/80 h) precipitated B2 TiFe  <100 nm in size. The orientation relationship was found to be ⟨100⟩A2//⟨100⟩B2, {100}A2//{100}B2, with a misfit of −6.1%. The alloy was found to be very hard (HV0.5 = 6.4 GPa) and strong (σy, 0.2 = 1.9 GPa) with a density of 6.68 g cm−3. TEM observation and micropillar deformation showed that the precipitates resist dislocation cutting.