Low Alloy Titanium: A Sustainable Alternative for Laser Powder Bed Fusion

Abstract

Additively manufactured (AM) α+β titanium alloys produced by laser powder-bed fusion (L-PBF) typically exhibit fine acicular microstructures due to the intrinsically fast-cooling rates of the process. In solute-rich alloys such as Ti-6Al-4V, this extreme grain refinement can severely reduce plasticity (fracture strains < 10%), thereby exposing parts to catastrophic engineering failures. In pursuit of a superior strength-ductility balance, we investigated the L-PBF processing of compositionally lean Ti-alloys containing small fractions of common iron and nitrogen solutes (beyond the standards of commercial purity). Despite their traditionally low wrought strengths, these near-purity alloys are shown to pair well with the grain refinement effects of L-PBF to produce mechanical properties on par with wrought Ti-6Al-4V (yield strengths > 825 MPa, fracture strains > 10%), indicating a strong compatibility with AM processing. Meanwhile these compositions are rare-metal free, and simple to recycle, thereby offering a cheap and sustainable alternative for use in titanium AM.