Towards uniform and enhanced tensile ductility of additively manufactured Ti−5Al−5Mo−5V−3Cr alloy through designing gradient interlayer deposition time

The thermal cycling of additive manufacturing can act as an in-situ intrinsic heat treatment (IHT), thereby producing spatially dependent microstructures and mechanical properties. This work demonstrates how to minimise the IHT effect to achieve uniform and enhanced tensile ductility of Ti−5Al−5Mo−5V−3Cr produced by laser powder bed fusion (L-PBF). It is found that the thermal cycling, in conjunction with substrate heating, can trigger the formation of isothermal ω and/or α phases in the β matrix, which leads to non-uniform and inferior tensile ductility. Ceasing substrate heating and/or increasing interlayer deposition time from 15 to 30 s enable substantial ductility improvement but fail to eliminate the ductility variation. Through designing a gradient interlayer deposition time (30 s – 45 s – 30 s), the tensile ductility increases 4–5 fold to ∼19% without any notable variation. The design strategy may help to tailor the microstructures and mechanical properties of other alloys which suffer from the same issue.