Texture effects on design of Mg biodegradable stents

ZM21 and AZ31B magnesium alloy tubes were hot extruded by a laboratory equipment in order to produce precursors for biodegradable stents. The microstructure and the texture evolution during the extrusion were investigated and related to the resulting mechanical properties. The tubes featured a homogeneous and refined equiaxed grain structure due to dynamic recrystallization experienced during the extrusion process. Electron backscattering diffraction analysis along the longitudinal section of the tubes revealed a typical ‘basal’ type texture featuring hexagonal basal plane aligned parallel to the longitudinal section of the tubes. Tensile and compression tests on different size of tubes showed a strong asymmetry in mechanical properties, the tensile strength being significantly higher than the strength measured in compression. Data about tension-compression behavior were related to crystallographic texture of samples and to the occurrence preferred {10–12} twinning in compression. The significance of the tension-compression behavior is analyzed in view of the application of the extruded tubes for biodegradable stents, especially considering the stages of expansion and scaffolding. The importance of considering the above effects in stent design and modeling is highlighted in order to improve performance and reliability of such devices.