The influence of bioactive hydroxyapatite shape and size on the mechanical and biodegradation behaviour of magnesium based composite

Abstract Reinforcement of hydroxyapatite in magnesium-based composites stands out due to their inherent properties, like, corrosion resistance, osteoconduction, and osteoinduction, apart from the compositional similarity with human bones. This study highlights the shape and size effect of bioactive HA ceramics on microstructural, mechanical, and biodegradation properties of the biocompatible Mg–3Zn based composites, fabricated via spark plasma sintering. Reinforcement of smaller size cylindrical HA (15 wt%) in Mg–3Zn matrix reduced the interparticle spacing. It generated comparatively higher constraint to the matrix deformation, which enhanced the hardness and elastic modulus by 23 and 16%, respectively, as compared to round HA. Qualitative behaviour of the plastically deformed indents was analysed via SPM imaging. Ultimate compressive strength of cylindrical HA reinforced composite enhanced by ~22 and 40%, when compared to round HA and Mg–3Zn composites, respectively, due to Hall-Petch strengthening. Reduction in the grain size of cylindrical HA reinforced composites increased the grain boundary area per unit volume, which facilitated the apatite precipitation sites in the physiological environment. Consequently, the corrosion resistance was enhanced by 63 and 27%, as compared to Mg–3Zn and round HA reinforced composite. The fabricated composite possesses superior biomechanical and biodegradation behaviour, rendering them potentially useful for temporary orthopaedic implants.