Study On The Content Of Sr Element And Heat Treatment Process For The Medical Biodegradable Mg-Zn-Zr-Sr Alloy

According to the service environment of bone screw and the particularity of position,in order to improve the corrosion resistance and mechanical property of biomedical magnesium alloy,We choose the biodegradable magnesium alloy to make the material of bone screw.As an essential trace element in human body,Sr has the function of preventing arteriosclerosis and preventing thrombosis.We design the Mg-Zn-Zr-Sr alloy with different content of Sr,and compare the mechanical properties、corrosion resistance and cytotoxicity,we can research the effects of different content of Sr element、solid solution and aging treatment on magnesium alloy.This study adopts the method of vacuum and inert gas protection smelting Mg-3.2Zn-0.8Zr-0.1Sr、Mg-3.2Zn-0.8Zr-0.3Sr and Mg-3.2Zn-0.8Zr-0.5Sr alloy,then it was annealed at 300 ℃ x 13 h.The ingot was extruded into the bar which are cut into Φ 8 mm×3 mm samples,then we can observe microstructure of samples by optical microscope to measure the grain size and analyze the composition of Mg-3.2Zn-0.8Zr-0.1Sr 、Mg-3.2Zn-0.8Zr-0.3Sr and Mg-3.2Zn-0.8Zr-0.5Sr alloy by X-ray diffractometer.In order to explore the mechanical property of the alloy,the bar was processed into tensile samples to test the tensile strength.The three electrode method was used to measure the polarization curve of the alloy.Study the mechanical properties and corrosion resistance by heat treatment process of solid solution and aging treatment.The degradation rate of magnesium alloy in vitro was measured by soaking experiment to measure pH value,Mg ion concentration and weigh loss.Finally,the cytotoxicity of three kinds of alloy was tested by the cell toxicity test.The results show that:1.The mechanical properties,corrosion resistance and biocompatibility of the Mg-3.2Zn-0.8Zr-0.3Sr alloy are the best.2.By contrast the mechanical properties and corrosion resistance of Mg-3.2Zn-0.8Zr-0.1Sr、Mg-3.2Zn-0.8Zr-0.3Sr and Mg-3.2Zn-0.8Zr-0.5Sr alloy after solid solution and aging treatment,we know that the most appropriate heat treatment process is homogenizing annealing at 300 ℃×13 h and solid solution treatment at 400 ℃x 2 h,at this point the mechanical properties and corrosion resistance is the best.3.In the experiment of immersion,the results of pH value、Mg2+ concentration and weight loss show the corrosion resistance of Mg-3.2Zn-0.8Zr-0.3Sr alloy after solid solution treatment is the best.4.In the cytotoxicity test,the cytotoxicity of Mg-3.2Zn-0.8Zr-0.3Sr alloy is the least。...