Effect of hybrid nano rare earth reinforcement and hot rolling on mechanical, corrosion, and biocompatibility of biodegradable Mg implants

Mg composites have emerged as promising materials for fabricating biodegradable implants, as their bone-like mechanical properties mitigate stress shielding effects and inherent biocompatibility facilitates healing. However, inadequate strength, limited ductility and rapid degradation constrain their clinical applicability. Microscale bioceramic reinforcements in Mg enhance strength but at the expense of ductility, while nanoscale reinforcements increase strength while retaining plasticity. In the present study, Mg composites containing metallic reinforcement (Ti, Zn, etc.), hybridised with synthesised nanoparticles (CeO₂, HA), were fabricated and investigated in both as-cast and hot-rolled conditions as potential biodegradable implant material. In as-cast composite, Ti addition achieved moderate strength improvements (55 % in YS and 30 % in UTS) but also improved elongation by 8.9 %, while Zn, Mn, and Ca addition improved strength significantly(146 % in YS and 58% in UTS), but reduced elongation. Hot-rolling further amplified strength and microhardness, with remarkable gains in HR-MHC/ZMC (236 % in YS, 106 % in UTS, and 81 % in microhardness). Electrochemical and static immersion studies on hybridised Mg composites revealed that alloying Zn, Mn, and Ca enhanced the polarization resistance by 148 % in AC-MHC/ZMC, but Ti increased H₂ evolution in AC-MHC/Ti. MTT assay with MG-63 cells revealed cell viability above 75 % and dual fluorescence staining confirmed healthy cell morphology.