Characterization of the α Phase Nucleation in a Two-Phase Metastable β Titanium Alloy

Beta titanium alloys are increasingly the best choice for automotive and aerospace applications due to their high performance-to-density ratio. Among these alloys, the TIMETAL Ti-LCB is already used in the automotive industry because it presents excellent mechanical properties and a lower cost compared with other Ti alloys. The current study deals with the characterization of the nucleation and growth of the alpha phase in several thermomechanical processes, because the distribution and size of the alpha phase strongly influence the mechanical properties of the resulting microstructures. Several heat treatments were conducted after either cold rolling or annealing. The resulting microstructures were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, or electron backscatter diffraction. It was observed that the morphology and the volume fraction of the alpha phase are strongly dependent on the holding temperature, on the heating or cooling rate, and on the beta grain size.