Processing of Mg–Ca/tricalcium phosphate composites and their electrochemical properties in a cell culture medium

Biodegradable magnesium-based composites have recently attracted considerable attention for use in orthopedic implants on account of not only their biocompatibility but also the possibility of tuning their mechanical and corrosion properties. In this study, the effects of the fraction of tricalcium phosphate (TCP) and its crystal structure on the electrochemical properties in Eagle's minimal essential medium as well as the mechanical properties were examined using high-strength Mg–Ca/TCP composites with a fine-grained matrix (grain size: 1.2 µm) and relatively uniform TCP particle dispersion. The composites were prepared by extruding mixtures of the component powders at 540 K and exhibited high compressive yield strengths exceeding 290 MPa. Electrochemical tests revealed that the corrosion parameters were insensitive to both the fraction of TCP particles and their crystal structure. The fine-grained matrix may have overwhelmed the ability of the TCP dispersion to serve as a corrosion inhibitor. The chemical compositions of the cracked surface layer on the matrix and the white discontinuous corrosion products of the composites formed after the electrochemical tests were similar to those of the parent alloy.