Study On Fine-grained Manufacturing And Controlling Mechanism Of Medical Zn-Mg Alloys

The standard electrode potential of zinc is between that of magnesium and ferroalloy,and zinc has suitable degradation rate and excellent biocompatibility,which is the focus of research in the field of biological materials.However,the application of zinc in medical field is limited by coarse grain size and low mechanical properties.Therefore,in order to refine the grain size of zinc alloys,improve mechanical properties and control the corrosion rate,different contents of magnesium were added to the zinc alloys.The effect of magnesium content on microstructure,mechanical properties and corrosion properties of cast Zn-Mg binary alloys was studied by smelting.On this basis,hot rolling process with different temperature was introduced to further refine grain size,improve mechanical properties and control corrosion rate,and the effect of rolling temperature on microstructure,mechanical properties and corrosion properties of the alloy was studied.The results show that the addition of alloying element magnesium in casting process can significantly refine the grain size of zinc alloy and improve the strength of the alloy.With the increase of magnesium content,the grain size decreases from 2000 μm of pure zinc to 21.5 μm of Zn-1.0wt%Mg alloy,and the ultimate tensile strength and fracture strain increase from 23.81 MPa and 0.17% of pure zinc to 209.58 MPa and 2.02%of Zn-1.0wt%Mg alloy.Fine grain strengthening,solid solution strengthening and second phase strengthening are the main strengthening mechanisms of as-cast Zn-Mg alloy.The corrosion rate of static immersion is consistent with that of electrochemical corrosion.The corrosion rate decreases first and then increases with the increase of magnesium content,and the corrosion rate of Zn-0.05wt%Mg is the lowest.When the magnesium content exceeds the solution,the corrosion pits appear in the eutectic structure,and the main chemical elements in the corrosion products are Zn,O,P,Na,Ca,Mg,K and Cl.The results show that the grain size of Zn-Mg alloy decreases with the increase of rolling temperature,but increases slightly with the increase of rolling temperature.When hot rolling temperature is between150℃ and 200℃,the deformation mode of Zn-Mg alloy is mainly twin deformation,while when hot rolling temperature is between 200℃ and250℃,the deformation mode of Zn-Mg alloy is mainly slip deformation.The ultimate tensile strength and fracture strain of all the hot-rolled alloys increased with the increase of rolling temperature,and the ultimate tensile strength of the alloys also increased with the increase of rolling temperature.In addition,the fracture strain of Zn and Zn-0.02wt%Mg alloys increased with the increase of rolling temperature,while the fracture strain of other alloys decreased with the increase of rolling temperature.The static immersion corrosion rate and electrochemical corrosion rate of Zn-Mg alloy after hot rolling have the same trend,and the corrosion rate increases first and then decreases with the increase of hot rolling temperature,and the Zn-Mg alloy after hot rolling at 200℃has the highest corrosion rate.Considering various properties of the alloy,the Zn-0.1wt%Mg alloy hot rolled at 200℃ has the best performance,with ultimate tensile strength up to 212 MPa and fracture strain up to 17.85%.The corrosion rate of Hanks reagent soaked for 14 days is 40.109 μm/year.The electrochemical polarization test showed that the corrosion rate was107.21 μm/year,which was more in line with the requirements of clinical application of biodegradable implanted scaffolds.