Partially degradable Ti-Mg composites for biomedical applications: Recent advances and future perspectives

Given the low elastic modulus, favorable bioactivity, and intrinsic biodegradability of Mg alloys, Ti-Mg composites comprising Mg embedded within a continuous Ti matrix are considered a promising alternative to conventional porous Ti alloys. During implantation, the Mg phase undergoes programmable degradation-mediated pore-formation, which synergistically promotes osseointegration and bone infiltration, while the retained Ti matrix provides mechanical support similar to that of porous Ti alloy implants. This review provides a comprehensive analysis of recent advancements in Ti-Mg composites, emphasizing their advantages as implant materials in terms of tunable microstructural architectures and performance optimization potential. First, advanced fabrication techniques, including powder metallurgy (PM), melt infiltration, and liquid metal dealloying (LMD), compatible with Ti-Mg composites are categorized and analyzed. Second, the macrostructure design principle and microstructural characteristics of Ti-Mg composites are reviewed. Subsequently, the corresponding properties of Ti-Mg composites-specifically, mechanical properties, degradation behavior, and both in vitro and in vivo biological evaluations-are systematically discussed. Finally, the challenges and future prospects of Ti-Mg composites are addressed. STATEMENT OF SIGNIFICANCE: Ti-Mg composites with partial degradation characteristics have emerged as a frontier research domain for next-generation bioactive metallic implants. The rapid evolution of advanced manufacturing technologies, particularly high-pressure solid-state sintering, additive manufacturing and liquid metal dealloying, has enabled unprecedented opportunities for biomimetic structural engineering, microstructure optimization, and performance enhancement in these hybrid systems. This review provides a comprehensive analysis of the processing-structure-property relationship in Ti-Mg composites, while critically evaluating current limitations and outlining potential development strategies. The aim of this work is to offer essential insights into bioactive metallic implants with region-specific degradation profiles, thereby facilitating their clinical translation through material innovation.