Morphing shield technology for chamber-free LW-DED in open atmosphere: a transformative approach to oxidation control for Ti-6Al-4V

This work demonstrates a chamber-free approach for fabricating high-quality Ti-6Al-4V using Laser Wire Directed Energy Deposition (LW-DED) supported by adaptive Morphing Shield Technology (MST). MST generates a self-regulating inert gas region that maintains oxygen levels below 20 ppm in open atmosphere, eliminating the need for a sealed build chamber. Process optimisation was conducted using single-bead trials and subsequently validated through thin-wall structures and a 500 mm conical build. Volumetric samples produced under MST exhibited an oxygen content of 0.15 wt.%, comparable to chamber-based LW-DED. Mechanical testing confirmed that the MST process delivers mechanical properties comparable to conventional chamber-protected LW-DED, with XY specimens achieving 998–1016 MPa ultimate tensile strength and 6.8–7.9% elongation, and Z specimens reaching 960–986 MPa ultimate tensile strength and 10.0–12.0% elongation. Microstructural analysis revealed clean basketweave α+β lamellar structures without oxidation films, and fracture surfaces exhibited uniform ductile microvoid coalescence. Together, these results establish MST as a viable solution for producing aerospace-grade Ti-6Al-4V entirely in open atmosphere.