Leveraging Fe/O dual-source in-situ alloying for a strong and ductile multiphase titanium
Description
To improve the strength and ductility of pure titanium, this study proposes a cost‑effective alloying strategy using Fe2O3 as a dual Fe/O source. Composite powders were fabricated via the layer-by-layer self-assembly (LBL) process to uniformly coat pure titanium particles with Fe2O3. Through optimization of laser powder bed fusion (LPBF) process parameters, quantitative and uniform O/Fe distribution was achieved. The non-equilibrium solidification conditions inherent to LPBF promoted a unique multi-phase network in Ti-O-Fe alloy. O element segregation at dislocation cores promotes Shockley partial dislocation slip on the HCP basal plane, transforming the stacking sequence to form an O-enriched intragranular FCC phase. Concurrently, Fe element segregation at grain boundaries induces a Fe-enriched BCC phase. This heterostructure led to an exceptional combination of an ultimate tensile strength of 795 MPa ± 1.4 MPa and a fracture elongation of 33.4% ± 0.5%. The high strength was attributed to oxygen solid-solution strengthening and grain refinement, whereas the excellent ductility originated from the coordinated deformation of the intragranular FCC and intergranular BCC phases, which effectively delayed strain localization. This work demonstrates a viable manufacturing route for fabricating low-cost, high-performance titanium alloys via coupled powder design and LPBF process control.