Simulation Of Degradable Character For Magnesium Alloys As Bio-Materials

Magnesium alloys have the character of low density, low modulus of elasticity and high specific stiffness, and its mechanical properties are close to the human skeleton. Magnesium has excellent biocompatibility and is an essential nutrient element for human. So it has good prospects as the biological material. Poor corrosion resistance of magnesium alloys provide a guideline for the development of biodegradable metallic materials in the medical field. As coronary stents or bone screws implanted in the human body and magnesium alloy degradably disappears with the healing of the implant site.The corrosion rate, corrosion kinetic characteristics and their impact factors of Mg-RE-l.OZr alloy as casting, solid solution state and solid solution+aging state are studied by single and bilateral corrosion test in simulated body Hank solution by using of weight loss method. The corrosion morphology is observed by scanning electron microscopy and the corrosion mechanism is analyzed. Moreover, the design and processing of the biological magnesium alloy stent have been disscussed.The results show that the average dynamic corrosion rate of Mg-RE-1.0Zr with casting state, solid solution state and solid solution+aging state specimen are 0.8848mg/(cm2·h), 0.1363mg/(cm2-h) and 0.1445mg/(cm2-h) measured by bilateral corrosion test. The average static corrosion rate are 0.5841mg/(cm2·h),0.0969mg/(cm2-h) and 0.1046mg/(cm2-h). At first, the corrosion speed obviously decreases with the corrosion time and finally tends to be stable. The dynamic corrosion rate is greater than that of the static corrosion rate. The unilateral simulation corrosion behavior is similar to that of the stent in human coronary artery and the corresponding average corrosion rate of solid solution+aging state is 0.1917 mg/(cm·h) and the corrosion rate is about 0.0688 mg/(cm2·h) after 168h corrosion. The unilateral corrosion rate is greater than that of the double-sided corrosion. The corrosion mechanism of the no-compression specimen grain is boundary corrosion and the pitting is the corrosion mechanism of the compressed specimen with solid solution+aging state.The recrystallization behavior of Mg-RE-1.0Zr specimens in solid solution+aging state compressed have been investigated and the recrystallization annealing temperature is determined to 350℃.