Effect of germanium and silicon additions on the mechanical properties of a near-α titanium alloy

The effect of Germanium (Ge) addition and simultaneous addition of Ge and Silicon (Si) on the tensile properties, impact toughness, and fracture behavior of the near-α alloy Ti-5Al-2Sn-4Zr-2Mo has been investigated at room temperature and at 650 °C. Addition of Ge monotonically increases the 0.2% yield stress (YS) and ultimate tensile stress (UTS) at both temperatures, and increases the rupture elongation at 650 °C; however, the Charpy impact toughness at both temperatures decreased. At 650 °C, this alloy ruptured in a hybrid manner, showing cracking at the germanide precipitates and plastic deformation in the surrounding matrix forming equiaxed dimples. The effect of simultaneous addition of 1 wt% Ge and 0.1 wt% Si on the mechanical properties is also discussed in relation to the effect of precipitate volume fraction and solid solution strengthening.