Tuning the strength and ductility of near β titanium alloy Ti-5321 by ω and O′ intermediate phases via low-temperature aging

The formation of intermediate phases omega and O' during low-temperature aging at 200 degrees C and its effect on plastic deformation in a new-developed near beta-Ti alloy Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe (wt %) have been studied in this work. The results showed that the omega 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 trade-off relationship of strength and ductility was overcome by the simultaneous precipitation of omega and O' phases. It was suggested that the omega and O' precipitation changed the deformation mechanisms, leading to this alloy exhibited different deformation behaviors and mechanical properties. With the quantities of omega and O' increasing, the strain-induced alpha '' martensite transformation was gradually suppressed, and the primary deformation mechanism changed into a mixture of strain-induced omega transformation, mechanical twining and dislocation slipping. These findings would provide an insight to achieve better combinations of strength and ductility in near beta-Ti alloys through tailoring the omega and O' phase transformations.

Automated summary

In this study, the formation of intermediate phases omega and O' during low-temperature aging in a new-developed near beta-Ti alloy was investigated. It was found that the precipitation of omega and O' phases changed the deformation mechanisms and mechanical properties of the alloy, leading to a better combination of strength and ductility by tailoring the phase transformations.