Synthesis and characterization of Mg-Zn-Mn-HA composite by spark plasma sintering process for orthopedic applications

This paper presents an investigation of design and development of low elastic modulus porous biodegradable Mg-Zn-Mn-HA composite for orthopedic applications via mechanical alloying and spark plasma sintering (MA-SPS) technique. The effect of MA-SPS process parameters like milling time, sintering temperature and sintering pressure have been studied on the structural porosity, elastic modulus and hardness of as-synthesized composite. The percentage of structural porosity was determined by Archimedes method and the elastic modulus and hardness of as-synthesized alloy were measured by the nano-indentation method. HA compound induced composite not only refined the grain but also enhanced porosity, which favoured osseointergation. The microstructure examination of the MA-SPS synthesized composite reveals the formation of high degree of structural porosity (15-25%), witnessed at low alloying time and high temperature. Sintering pressure enables pores reduction and induces an additional driving force for the compaction and sintering temperature assists the powder particles to coalesce, which subsequently reduces the porosity, densified the compact, and enhanced the mechanical properties. XRD pattern analysis confirmed the formation of MgCaO, β-TCP, Mn-CaO, and Ca-Mg-Zn phases, enhanced mechanical properties and corrosion characteristics. The degradation rate of Mg-Zn-Mn-HA alloy was reduced from 1.98 mm/year to 0.97mm/year by the alloying of HA elements.