Electrochemical Properties Of Fe-based And Mg-based Alloys For Biomedical Applications

Fe-based biomaterials are considered as a new generation of vascular scaffold materials to replace permanent plant materials for its good mechanical properties, biocompatibility, safety and non-toxicity. However, the most important problem that limits the application of Fe-based biomaterials as biodegradable materials is that the degradation rate is too slow, which is close to the permanent implant material.The Portevin–Le Chatelier(PLC) effect was observed by the traditional tensile test and Gleeble thermal simulation compression experiment of the specific magnesium alloy. Many properties of the material are affected by the PLC effect. It increases the flow stress, the ultimate tensile strength and the working hardening rate of the material and it reduces the ductility and fracture toughness of the sample. Researchers have carried out extensive and in-depth studies on the mechanism of PLC effect, of which the most common one is that the dynamic strain aging effect. However, the study about the PLC effect on the electrochemical performance of the alloy is very rare.In this paper, Fe-20Mn-1.2C alloy was selected to improve the performance of Febased alloy by accumulative rolling with liquid nitrogen and annealing. The results show that the stacking of liquid nitrogen can effectively cause the accumulation of dislocations, resulting in a large number of vacancies and slip band defects, and the second phase particles produced by annealing process are first obtained from these defects and numerous corrosion micro batteries are formed, greatly accelerating the corrosion rate of Fe-20Mn-1.2C alloy.The effect of PLC on the electrochemical properties of magnesium alloy was studied on Mg-6Y-Nd-2Zn alloy, and the difference between the dynamic electrochemical performance and the static electrochemical performance was compared. The results show that the PLC effect increases the corrosion rate of magnesium alloy, and the dynamic electrochemical corrosion rate is higher than that of the static electrochemical one. This is due to the process of the PLC effect, where the atomic dislocations and vacancy were generated. The generation of dislocations hinders the diffusion of solute atoms, and with the increase of deformation, the solute atoms will break through the dislocations, resulting in the instability of the the alloy surface. However, for the samples which PLC effect has already occurred, there is no external force existence. The interior of the alloy is balanced and stable. So the electrochemical properties between the two situations are obvious different.