Processing and Properties of a New Biodegradable Mg−Zn−Ca−Zr Alloy

Magnesium alloys are used for degradable orthopaedic and cardiovascular implants due to their favourable mechanical and biological properties, degradation ability in physiological environment and stimulatory effect on the new bone formation. The research challenges are related to the increase of biological and mechanical compatibility. For the present study, a magnesium based alloy design was conducted to the following chemical composition: Mg-2.7Zn-1Ca-0.6Zr (wt.%). A complex thermomechanical processing route was applied: a plastic deformation by extrusion at various temperatures and deformation degrees (400 degrees C-480 degrees C, E=20%-40%), followed by various final heat treatments at 200 degrees C-400 degrees C for 10min-60min. Further, the influence of processing parameters upon the structure, mechanical properties and biological response was studied. Processed specimens were characterized by scanning electron microscopy (secondary electron imaging and energy dispersive spectroscopy) and mechanically by tensile tests. The most representative results were obtained for the samples extruded at 450 degrees C/E=20%, followed by a final heat treatment at 350 degrees C/15min, air cooling. Further, for samples which revealed promising results, in-vitro testing was developed. Biocompatibility testing of the Mg-2.7Zn-1Ca-0.6Zr (wt.%) alloy was realized by indirect contact studies using the Vero (ATCC (R) CCL-81, American Type Culture Collection) cell line. Cells morphologies, cell viability and proliferation were evaluated.