Effects of oxidation and boron addition on tensile creep properties of cast Ti–46Al–2V–1Cr based alloys

Creep behaviours of Ti–46.5Al–2.5V–1Cr (at.%) and Ti–46.2Al–2V–1Cr–0.5B–0.4Ni alloys were investigated at 750 °C under constant stresses of 200 and 120 MPa, respectively, both in air and in vacuum. A well-defined steady state was achieved for Ti–46.5Al–2.5V–1Cr tested in vacuum. However, the specimens tested in air and those of Ti–46.2Al–2V–1Cr–0.5B–0.4Ni generally showed a lack of steady state deformation. Although the secondary creep rates were comparable for Ti–46.5Al–2.5V–1Cr, the total creep life was much shorter for the specimens tested in air compared to those tested in vacuum. For Ti–46.2Al–2V–1Cr–0.5B–0.4Ni, the secondary creep rate was increased and creep life much shortened when tested in air. Compared to Ti–46.5Al–2.5V–1Cr, the boron containing alloy exhibited much reduced creep resistance in terms of secondary creep rate and the total creep life irrespective of the testing environment. It is concluded that oxidation and addition of B both have considerably detrimental effects on creep strength of the material.