The Role of Minor Oxygen on Tensile Propertiesin Cast Ti-6Al-4V Alloy

In this paper, the effect of oxygen content in the range of 0.15 ~ 0.44 wt.% on the mechanical properties at room temperature of cast Ti-6Al-4V alloy was studied, and the mechanism of oxygen effect on its tensile deformation behavior was discussed. The results show that with the increasing of oxygen content, the strength of the alloy increases, while the elongation increases first and then decreases. It is found that oxygen solution in α-Ti leads to obvious change of lattice parameter c/aratio. The activation of prismatic slip of α-Ti will bring oxygen atoms from octahedral site to hexahedral site to reduce stacking fault energy. The reason why the strength of cast Ti-6Al-4V alloy increases and the ductility decreases with the increasing of oxygen content is that the lattice distortion caused by the solid solution of oxygen inα-Ti prevents the dislocation motion, while the abnormal ductility increasing at 0.22 wt.% oxygen content is due to the dislocation shuffling oxygen atoms into the hexahedral site.