Design Optimization and Surface Modification of Biodegradable Magnesium Alloy AZ91 for Biomedical Implants Using Electrical Discharge Machining

Abstract

Magnesium alloy AZ91, known for its lightweight nature, biocompatibility, and controlled biodegradability, is a promising material for orthopedic implants. However, faster corrosion in a physiological environment remains a challenge. This work investigates Electrical Discharge Machining (EDM) with copper and brass electrodes in a kerosene dielectric to optimize the surface roughness, hardness, and corrosion resistance of AZ91. Electrochemical deposition of copper and brass coatings was also performed to modulate the degradation rate. Surface assessment through Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) indicated that optimizing EDM parameters greatly improved the surface quality, which was characterized by less roughness and higher hardness. Of the coatings, copper exhibited better corrosion resistance, which slowed down the degradation of AZ91 in simulated body fluid (SBF). Therefore, this combination of EDM with electrochemical deposition opens up the possibility of developing patient-specific implants with controlled degradation rates, which ensures mechanical support during healing and avoids follow-up surgeries. This work paves the way for next-generation bioresorbable implants, effectively providing a bespoke solution to orthopedic applications integrating precision machining and surface engineering techniques.