Advances in TNZT Alloys for Biomedical Applications: Mechanical Performance, Tribological Behavior, and Surface Modification Strategies

The development of next-generation biomaterials is essential for improving the performance, longevity, and biocompatibility of medical implants. Titanium-Niobium-Zirconium-Tantalum (TNZT) alloys have emerged as a promising class of metallic biomaterials due to their non-toxic elemental composition, low elastic modulus, and favorable corrosion resistance under physiological conditions. Unlike traditional alloys such as Ti-6Al-4V, TNZT alloys exhibit improved biomechanical compatibility and reduced risk of stress shielding. This review provides a comprehensive overview of TNZT alloy systems, focusing on the influence of compositional variations and the addition of Si, Zn, Fe, Mn & Ag elements on their mechanical strength, elastic behavior, and wear resistance. The article also discusses tribological challenges and the importance of surface engineering techniques such as laser nitriding and physical vapor deposition (PVD) coatings to enhance osseointegration and antibacterial properties. Furthermore, it examines the deformation mechanisms, dislocation activity, and the role of β-phase stabilization in improving performance. This article outlines the future directions for TNZT-based materials in orthopedic and dental implant applications, providing insights into their clinical translation and long-term functionality.