Mg based implants are limited by their poor strength, ductility, and corrosion performance in physiological environments, drawbacks further compounded by their premature loss of mechanical integrity and evolution of harmful hydrogen gas. Neodymium additions to magnesium have been shown to improve mechanical properties through precipitation and solid solution hardening. Therefore, the present study incorporated Nd additions (up to 3%) into a promising Mg-5%Zn-0.13%Y-0.35%Zr alloy to improve mechanical properties and corrosion resistance. The microstructure evaluation of a series of alloys was performed using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction analysis. The mechanical properties were examined in terms of hardness and tensile strength. Corrosion behavior was evaluated by immersion testing, impedance spectroscopy analysis, potentiodynamic polarization and stress corrosion examination using slow strain rate testing (SSRT), all in PBS solution. The results indicate optimal strength, ductility and corrosion performance with a 2% Nd addition. This was explained in terms of secondary phase formation of a W-phase (Mg 3 (Nd,Y) 2 Zn 3) and T-phase (Mg 4 (Nd,Y)Zn 2).
Mg alloys are attractive as a structural material for biodegradable implants due to their mechanical properties, biocompatibility and degradation capability in physiological environments. However, their accelerated corrosion degradation, coupled with their inherent sensitivity to stress corrosion, can cause premature failure and consequently loss of mechanical integrity. This study aims to evaluate the potential of a Mg-5% Zn alloy with up to 3% Nd as an implant material in terms of stress corrosion performance in in vitro conditions. Stress corrosion behavior was evaluated under static loading conditions using slow strain rate testing (SSRT) analysis and under low cycle corrosion fatigue (LCCF). Both the SSRT analysis and LCCF testing were carried out in a simulated physiological environment in the form of a phosphate-buffered saline (PBS) solution. The obtained results indicate that the addition of up to 3% Nd to Mg-5% Zn alloy did not have any substantial influence on the stress corrosion susceptibility, beyond the inherent different mechanical properties of the tested alloys. This was attributed to the limited effect of the Nd on the passivation layer and due to the fact that the secondary phases produced by the Nd additions—W-phase (Mg3(Nd,Y)2Zn3) and T-phase (Mg4(Nd,Y)Zn2)—did not create any substantial micro-galvanic effect.
The article In Vivo Evaluation of Mg-5%Zn-2%Nd Alloy as an Innovative Biodegradable Implant Materialwritten by Elkaiam et al. was originally published electronically on the publisher's internet portal (currently SpringerLink) on September 17
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.