Study on the formation mechanism of α lamellae in a near β titanium alloy

In order to obtain more insight in the two existing mechanisms on the nucleation, i.e., sympathetic nucleation and interface instability nucleation, of α lamellae in the near β Ti alloys, the micro-texture of α lamellae in Ti-7Mo-3Nb-3Cr-3Al has been investigated by using electron backscatter diffraction (EBSD). The results show that the αWGB lamellae can not only grow up from αGB grains by inheriting the orientations but also sympathetically nucleate at the αGB/β interface during the slow cooling process. These observations provide the first direct experimental evidence that the formation mode of α lamellae in Ti-7333 alloy consists of sympathetic nucleation and interface instability nucleation. Based on the present results together with some previous studies on α phase transformation in Ti-based alloys the influence of β-stabilizers parameter on the change of formation mechanism of α lamellae was discussed.