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This study presents a novel approach for the fabrication of commercially pure titanium (CP–Ti) components. The approach conferred superb strength to CP-Ti without sacrificing its ductility. A yield strength of 807 MPa combined with 19.15% elongation was realized through selective laser melting (SLM) by using a high-power laser and incorporating solute atoms from the Ar−N 2 reactive atmosphere. Mechanical properties and microstructures of the as-printed CP-Ti were systematically investigated. Transmission electron microscopy, electron backscatter diffraction, and atom probe tomography were employed to reveal the mechanism underlying the in-situ reaction between CP-Ti and the reactive atmosphere. Results suggest that nitrogen generally dissolved in the α′-Ti matrix as interstitial solute atoms. The beneficial N content has a critical limit of ∼0.43 wt%. The ductility of CP-Ti will decrease drastically if its N content exceeds this limit. A constitutive model was developed for describing the tensile deformation behavior of the in-situ strengthened CP-Ti over various solute contents and grain sizes. This work demonstrates a promising methodology for the fabrication of high-performance metallic components and extends the fundamental understanding of SLM process under the reactive atmosphere.

To realize near net-shaping of hard-to-process intermetallics is an often challenging but critical issue to their wider industrial applications. In this work, we report that an intermetallic Ti-22Al-25Nb has been successfully fabricated by selective laser melting (SLM). The as-printed samples show a high room-temperature ultimate tensile strength ~1090 MPa and excellent ductility ~22.7%; both values are higher than most conventionally fabricated Ti-22Al-25Nb intermetallic. We clarify the mechanical performance achieved by detailed microstructure analysis, including dislocation analysis and phase constitution analysis. High-density dislocation networks significantly contribute to the strength and ductility, which are further enhanced by the favorable phase constitution, including the nano-scale O phase precipitates within the disordered β phase and disappearance of the brittle α2 phase in the microstructure. Phase evolution during SLM has also been clarified using in situ heating, high-temperature synchrotron X-ray diffraction and Scheil simulation, particularly regarding the O phase's formation. It is demonstrated that O phase is formed by shearing primary cubic B2 phase along (110)[111] direction into an orthorhombic structure under high residual stress. Furthermore, a demonstrative part of turbine blade has been fabricated to highlight the importance of SLM in fabricating critical structural part like the hard-to-process intermetallics.