Growth behavior of α phase in Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.7Nd titanium alloy

The thermal stability of the microstructure of a near-alpha titanium alloy after aging at 750 degrees C was investigated using optical microscope and transmission electron microscope as well as composition analysis. Aging treatment brings about significant coarsening of grain boundary alpha and alpha 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 alpha Widmanstatten plates were coarsened due to the movement of alpha/beta interface for Widmanstatten microstructure, and the phase boundaries of primary alpha (alpha(p)) phase directly moved into the transformed beta for bimodal microstructure.