Abstract: The thermal stability of the microstructure of a near-α titanium alloy after aging at 750℃ was investigated using optical microscope and transmission electron microscope as well as composition analysis. Aging treatment brings about significant coarsening of grain boundary α and α platelets within the colonies for martensitic microstructure. The observed changes are related to the growth steps or ledges of the interface and lamellar termination presented in the microstructure. The composition analysis of the coarsened $\alpha$ plate is consistent with the growth kinetics. The α Widmanstätten plates were coarsened due to the movement of α/β interface for Widmanstätten microstructure, and the phase boundaries of primary α (αp) phase directly moved into the transformed β for bimodal microstructure.

Key words: Near-α titanium alloy, Microstructure, Coarsening, Aging