Investigation of mechanical properties and biocorrosion behavior of in situ and ex situ Mg composite for orthopedic implants.

In the present study, the biocorrosion and mechanical properties of in situ and ex situ ZK60 matrix composites were investigated. For this purpose, ex situ composite samples containing 10 and 20 vol% SiC particles were prepared by stir casting method, while the in situ composite samples were produced by precipitation hardening at 175 °C and 225 °C. Microstructural examinations confirmed the homogeneous distribution of reinforcements and precipitations for ex situ and in situ composites, respectively. Moreover, the ex situ composites had higher hardness than the in situ composites due to the presence of ceramic particles. The samples were subjected to potentiodynamic polarization and electrochemical impedance spectroscopy in the SBF solution. The results showed that ex situ composites had a higher corrosion rate than in situ composites. The results of the MTT assay displayed that all samples had acceptable biocompatibility. Additionally, SEM micrographs obtained after immersion of both composites in the SBF solution for 7 and 28 days showed the formation of the hydroxyapatite layer on the surface of the samples. Both composites showed almost excellent wear resistance, and SEM micrographs approved that abrasive wear and adhesive wear were the dominant mechanisms for ex situ and in situ composites, respectively.