Design and additive manufacturing of low-Young's-modulus β-titanium alloys for biomedical applications: from alloying theory to scaffold engineering

β-titanium (β-Ti) alloys are promising materials for biomedical implants due to their excellent biocompatibility and intrinsically low Young's modulus, which reduces stress shielding compared with conventional α- and α+β-Ti alloys. With advances in additive manufacturing (AM), laser powder bed fusion (LPBF) is increasingly used to fabricate near-net-shape implants and scaffold structures, which can further reduce the Young's modulus. This paper comprehensively reviews the design and fabrication of β-Ti alloys with low Young's modulus, focusing on the alloy design, manufacturing of products via LPBF, and their joint effects on the regulation of Young's modulus. Specifically, β-Ti alloy design principles are systematically reviewed, focusing on the optimization of chemical composition, microstructural control, and emerging methodologies for predicting and tailoring mechanical properties. Furthermore, the influence of LPBF processing parameters and strategies on microstructure, texture, and mechanical properties is introduced, highlighting current achievements in the modulation of Young's modulus from the aspects of alloy fabrication. As a key advantage of AM, particular attention is given to the manufacturing of complex scaffold structures, which enable the regulation of wide-range stiffness through structural design. Moreover, challenges and limitations of β-Ti alloys with low modulus in the aspects of alloy design, LPBF, and design of scaffold structures are discussed. Overall, this review demonstrates state-of-the-art achievements on the fabrication of low-modulus β-Ti alloy via LPBF, providing systematic insights on the manufacturing of next-generation orthopedic implants with high precision and outstanding properties.