Investigation of magnesium-based alloys for biomedical applications

In this work, cast, as well as wrought, Mg-based alloys and pure Mg were investigated as promising materials for construction of biomedical degradable implants. Mg, AZ91, AM50 and MgCa5 alloys were studied. The alloys were prepared by various routes including casting into large sand or small metal moulds and hot extrusion. Microstructures and basic mechanical properties of the alloys were investigated. Chemical properties which are useful to predict the degradation rates of implants were determined by exposition tests in a model saliva solution. It was shown that the microstructures of the wrought materials contained recrystallized grains of alpha(Mg) phase and intermetallic phases. These microstructures were more uniform than those of the cast alloys which contained more or less continuous network of interdendritic phases around primary alpha(Mg). The presence of the network led to a reduction of strength of the cast alloys. Exposition tests showed that the cast AZ91Fe0.05 alloy corroded most rapidly in the model saliva. Its corrosion rate was sufficient for medical applications. The fine microstructure of this alloy resulted in a relatively uniform corrosion attack despite the high iron amount.