Tuning the Strength and Ductility of Near Β Titanium Alloy by Ω and O′ Intermediate Phases Via Low-Temperature Aging

Abstract

The formation of intermediate phases ω and O′ during low-temperature aging at 200 °C and its effect on plastic deformation in a near β-Ti alloy Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe have been studied in this work. The results showed that the ω and O′ phases were continuously transformed upon aging, and larger amount of O′ precipitates was developed in air-cooled sample than water-quenched one. Upon early aging the yield strength and ductility of alloy were simultaneously improved until 60 min. The embrittlement of ω phase was overcame by the precipitation of O′ phase. It was suggested that the ω and O′ precipitates changed the deformation mechanisms, leading to this alloy exhibited different deformation behaviors and mechanical properties. With the quantities of ω and O′ increasing, the strain-induced α′′ martensite transformation was gradually suppressed, and the deformation mechanisms changed into strain-induced ω, twining and dislocations slipping mixture. These findings would provide an insight to achieve better combinations of strength and ductility in near β-Ti alloys through tailoring the ω and O′ phase transformations.

Keywords: Titanium alloy, Low-temperature aging, ω and O′ phases, deformation mechanism, Mechanical properties