Tailoring Zr-based bulk metallic glasses with noble metals: Toward next-generation biocompatible implants

The development of biocompatible and mechanically robust materials for long-term implant applications remains a central challenge in biomedical engineering. This research introduces a series of Ni-and Be-free Zr66.5M16.5Al10Fe5Ti2 bulk metallic glasses (BMGs; where M = Cu, Pt, Au, and Pd) that were designed and synthesized with the aim of overcoming the cytotoxic limitations associated with conventional Zr-based BMG systems. Structural investigations using X-ray diffraction and transmission electron microscopy on 2-mm suction-cast rods confirm the fully amorphous nature of the Cu-, Pd-, and Pt-containing alloys, while the Au-containing counterpart exhibits partial nanocrystallinity. Thermal characterization reveals a high glass-forming ability and extended supercooled liquid regions, particularly for Pt-and Pd-substituted systems. Mechanical testing demonstrates that the Zr-Pt alloy exhibits the highest hardness (7.17 GPa) and compressive strength (1767 +/- 35 MPa). In contrast, the Zr-Au alloy shows superior plastic strain (-4 %), ascribed to greater free volume and a minor fraction of-5-10 nm nanocrystallites. The corrosion performance in 3.5 wt% NaCl solution was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy, indicating significantly improved passivation and pitting resistance for the Pt-and Pd-bearing alloys. Altogether, the findings highlight that partial substitution of Cu with noble metals enables tailored mechanical and electrochemical properties, positioning these novel Zr-based BMGs as promising candidates for next-generation implantable devices.