Precipitation of α phase and its morphological evolution during continuous heating in a near β titanium alloy Ti-7333

In this work, β-quenched Ti-7333 was slowly heated to different temperatures to investigate the precipitation behavior of α phase. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were used to characterize the microstructures and orientation relationships (ORs) between the precipitates and the β matrix. The results show that isothermal ω (ω_iso) phase with an ellipsoidal morphology holds the OR with α phase characterized by [0001]_α // [21¯1¯0]_ω, (101¯0)_α // (011¯0)_ω, and assists the nucleation of α phase. The lattice misfit of ω/β interface is determined to be about 2.824%, which contributes to the development of α phase. With the assistance of ω phase, fine-scaled α precipitates with high density can be obtained within β matrix. The α variants obey the Burgers orientation relationship (BOR) with respect to β matrix, and the lattice misfit at α/β interface is determined to be about 5.340%. Eventually, the morphological evolution of the α precipitates during continuous heating is summarized. The results of the present work could provide a practical information for a better understanding of the precipitation behavior of the α phase during heating in near β titanium alloys.