Abstract: Metastable β titanium alloy Ti-10V-2Fe-3Al with α+β dual-phase has found applications in the aerospace industry because of its high strength and good toughness, and the mechanical behavior and microstructural evolution in the alloy have been key issues for numerous investigations. In the present study, we meticulously investigate the dynamic elastic modulus of dual-phase Ti-10V-2Fe-3Al alloy during cooling and report an anomaly in the elastic modulus of the alloy upon cooling. The elastic modulus anomaly is manifested as a continuous softening of the elastic modulus which deviates from Wachtman's equation within a temperature range from 350 K to 200 K. By nanoscale microstructure characterizations, it is demonstrated that such elastic modulus anomaly is closely associated with the strain glass transition characterized by frequency-dependent modulus, invariance of average structure, the formation and growth of nanodomains, and non-ergodicity effect. In aging treatment, the precipitation of α phase enhances the stability of the β matrix and suppresses the long-range ordered martensitic transformation into strain glass transition, giving rise to a continuous decrease of the elastic modulus of the β matrix. This work could be helpful for understanding the evolution in mechanical properties and microstructures of metastable β titanium alloys with α+β dual-phase, shedding light on the research and development of advanced metastable β titanium alloys.

Key words: Ti-10V-2Fe-3Al alloy, Microstructural evolution, Elastic modulus anomaly, Strain glass transition, Nanodomains