HPHT treatment enables superior strength–ductility synergy in selective laser melted commercially pure titanium

Selective laser melting (SLM) provides a route to produce high-strength pure titanium, but the ductility of as-fabricated material is often limited by printing-induced pores, lack-of-fusion defects and heterogeneous solidification microstructures. In this study, high-pressure high-temperature (HPHT) treatment was investigated as a pressure-assisted post-processing strategy to tailor pore characteristics, defect structures and tensile properties in SLM pure Ti. Among the processing conditions examined, treatment at 5 GPa and 500 °C for 5 min produced the best strength–ductility balance. The detectable porosity decreased from 2.83% to 0.08%, while the yield strength increased from approximately 700 to 1000 MPa and the elongation improved from approximately 1% to 19%. X-ray diffraction confirmed that the matrix remained dominated by hcp α-Ti, with no detectable β-Ti, ω-Ti or secondary precipitates within the detection limit of laboratory XRD. The improved mechanical response was mainly associated with coupled defect elimination and defect-structure regulation. GPa-level pressure promoted pore closure and suppressed defect-driven premature fracture. Meanwhile, dense dislocation substructures and 10–50 nm deformation twins provided additional barriers to dislocation motion and promoted local strain accommodation. These results demonstrate HPHT treatment as an effective non-alloying post-processing route for optimizing the strength–ductility balance of additively manufactured pure titanium through coupled defect elimination and defect-structure regulation.