Tailoring bimodal structure for high strength and ductility in pure titanium manufactured via laser powder bed fusion

Laser-powder bed fusion (L-PBF) is being increasingly employed in the fabrication of commercially pure titanium (CP-Ti) components for biomedical applications. However, L-PBF-manufactured CP-Ti parts typically exhibit high strength and reduced ductility owing to the formation of acicular α′ martensite. It is essential to decompose the acicular α′ martensite into the equilibrium α phase through post-heat treatments to achieve superior mechanical properties. In this study, post-heat treatments were applied to L-PBF-fabricated CP-Ti Gr. 1−Gr. 4 samples. The microstructures of the as-fabricated CP-Ti samples were dominated by acicular α′ martensite, which exhibited high strength (>800 MPa) but low ductility (30%) in the Gr. 1 and Gr. 2 samples, but low ductility (700 MPa for Gr. 2 and,>850 MPa for Gr. 4) and high ductility (>35% for Gr. 2 and Gr. 4), which are superior to those of the samples processed under full annealing conditions. Therefore, tailoring the bimodal structure in the L-PBF-manufactured CP-Ti for both high strength and ductility is promising for biomedical applications. •Bulk CP-Ti Gr. 1−Gr. 4 were produced using selective laser melting.•As-fabricated CP-Ti exhibited high strength and low ductility.•Equiaxed and bimodal structure were achieved by post-heat treatment.•The bimodal structures provided higher σ × ε values than equiaxed grains.