Electropulsing-assisted chemical boundary engineering to achieve strengthening and toughening of Ti-6Al-4V alloy manufactured via laser powder bed fusion

Abstract

Conventional post-processing techniques, such as hot isostatic pressing and heat treatment, often encounter difficulties in achieving an optimal balance between high strength and ductility in additively manufactured titanium alloys. This study presents an electropulsing-assisted chemical boundary engineering technique to address this challenge in the Ti-6Al-4V alloy prepared via laser powder bed fusion (LPBF). This innovative process establishes chemical boundaries within the prior-β grains through controlling element diffusion at elevated temperatures, resulting in a novel bi-lamellar martensitic microstructure. The technology yields a high yield strength of ∼1118 MPa and an elongation of ∼11.2 % in LPBF-fabricated Ti-6Al-4V alloy. The enhanced yield strength is attributed to the presence of chemical boundaries that impede dislocation slip. Additionally, these chemical boundaries restrict the growth of α′ and inhibit the propagation of microcracks, leading to a significant increase in elongation. This innovative process is anticipated to be an effective method for enhancing the mechanical properties of various additively manufactured α+β titanium alloys.