RESUMEN
BACKGROUND: As a metal internal fixation material, magnesium alloy has more unique advantages, such as biodegradability and elastic modulus. The elastic modulus of magnesium alloy is similar to the compact bone,which is enough to avoid stress-shelter effect. However, biological activity represents bonding ability with the bone in the body for fracture fixation materials, which is of great significance for studies on new kinds of magnesium alloys.OBJECTIVE: To observe the microstructure of Mg-Zn-Gd alloys and to analyze the corrosion products on the material surface after immersed in simulation body fluid.METHODS: The Mg-Zn-Gd alloys were manufactured by the method of fusion casting. Scanning electron microscope with spectrometer was applied to observe microstructure and distribution of precipitated phase and corrosion products of Mg-Zn-Gd alloys in simulated body fluid.RESULTS AND CONCLUSION: The Mg-Zn-Gd alloy was composed of α-Mg solid solution containing Gd and Zn elements and eutectic structure. The eutectic structure was almost feathery, oval-shaped, herringbone-shaped and strip-shaped along the grain boundary. The main ingredients of eutectic structure included Mg, Zn and Gd elements.Deposition layer was composed of O, Mg, Ca and P elements on the surface of Mg-Zn-Gd alloy after 72 hours soak in Hank's solution. X-ray diffraction analysis showed that film layer contained Mg(OH)2 phase, which promoted calcium salt deposition and reduced the corrosion rate. So Mg-Zn-Gd alloy can obtain better biological activity.