Mechanical and degradation behaviour of biodegradable magnesium–zinc/hydroxyapatite composite with different powder mixing techniques

Magnesium-based biomaterials have recently gained great attention as promising candidates for the new generation of biodegradable implants. This study investigated the mechanical performance and biodegradation behaviour of magnesium-zinc/hydroxyapatite (Mg–Zn/HA) composites fabricated by different powder mixing techniques. A single step mixing process involved mechanical alloying or mechanical milling techniques, while double step processing involved a combination of both mechanical alloying and mechanical milling. Optimum mechanical properties of the composite were observed when the powders were prepared using single step processing via mechanical alloying technique. However, Mg–Zn/HA composite fabricated through single step processing via mechanical milling technique was found to have the most desirable low degradation rate coupled with highest bioactivity. The composite achieved the lowest degradation rate of 0.039 × 10−3 mm/year as measured by immersion test and 0.0230 mm/year as measured by electrochemical polarization. Ca:P ratio of the composite also slightly more than enough to aid the initial bone mineralization, that is 1:1.76, as the required Ca:P ratio for initial bone mineralization is between 1:1 and 1:1.67. Keywords: Magnesium-based composite, Biodegradable implant, Powder metallurgy, Mechanical alloying, Mechanical milling