Simultaneous enhancements of strength and ductility of additively manufactured Ti-6.9Al-6.8Zr-2.3Mo-2.2V alloy by cyclic heat treatment and solution-aging.

In the paper, in terms of the new developed additively manufactured Ti-6.9Al-6.8Zr-2.3Mo-2.2V alloy, different microstructural design strategies were proposed to tune the morphology and content of α phase to optimize the mechanical properties of the alloy and the corresponding deformation mechanism of the alloy were characterized and analyzed. The results show that after cyclic heat treatment and solution-aging, the best comprehensive mechanical properties (yield strength ∼ l009 MPa, and elongation ∼12%) are obtained. The better comprehensive tensile properties are attributable to the microstructure consisting 16% equiaxed α p and β t structure. The cycle heat treatment can effectively decrease the length-width ratio of lamellar α phase and improve spheroidization of primary α phase. The equiaxed primary α phase has higher ability to coordinate local plastic strain, leading to the activation of extensive prismatic <a> slip and improving the ductility of the alloy. After aging-solution, large amount of fine α s precipitate from β phase. The high hetero-deformation induced stress at α s /β interfaces in β t structure promotes the activation of the pyramidal <a> slip systems, thereby increasing the yield strength. The present findings provide significant guidance for additive manufactured titanium alloy having good combination of tensile ductility and strength. • In terms of the new developed additively manufactured Ti-6.9Al-6.8Zr-2.3Mo-2.2V alloy, different heat treatments were proposed to improve the mechanical properties. The best matching of strength and ductility (yield strength ∼ l015 MPa, and elongation ∼10.5%) was obtained after cyclic heat treatment and solution-aging. • Owing to the high hetero-deformation induced stress at αs/β interfaces, the pyramidal <a> and <a + c> slip systems were operated, resulting in an increase of yield strength. • The prismatic <a> slip plays a dominant role in accommodating the external strain and promoting deformation. [ABSTRACT FROM AUTHOR]