Study On Surface Ion Beam Modification And Corrosion Resistance Of WE43 Biological Magnesium Alloy

Bio-magnesium alloy has an elastic modulus and degradable characteristics that match the human body,and is an ideal material for implants.However,because magnesium alloy corrodes too fast,it greatly limits its promotion and use in the medical field.In this paper,two kinds of surface treatment methods,ion implantation and ion coating,were used to prepare nano scale implantation layer and micron scale coating layer on WE43 alloy.The effects of different implantation dose and deposition time on the surface morphology,structure,corrosion resistance and hardness of WE43 alloy were systematically investigated.The analysis and conclusions are as follows:(1)After the four elements of Fe,Zn,Ti and Zr were implanted in different doses on the surface of WE43 alloy,XRD and XPS analysis showed that the modified layer was composed of Mg,MgO,implanted elements and their oxides.The electrochemical test on the sample after ion implantation shows that Fe ion implantation will accelerate the corrosion rate of the substrate,and as the implantation dose increases,the corrosion rate of the alloy will increase.When Zn ions are implanted at a dose of 5×10¹⁶ ions·cm^-2,the alloy has a lower I_corr value,which is 47.2%lower than that of WE43 alloy,and has better corrosion resistance.However,the I_corr values of the alloys at other implantation doses are not much different from those of the matrix.The Ti implanted alloy and Zr implanted alloy significantly reduce the I_corr values.Especially when the implantation dose is 1×10¹⁷ and 5×10¹⁶ ions×cm^-2,the alloys have the smallest I_corrvalues.The degradation speed of the alloy is related to the compactness and chemical activity of the film.The loose and porous Fe₂O₃ phase makes the film not dense enough,forming micro-galvanic corrosion and accelerating the corrosion.And Zn,Ti,Zr ion implantation forms a dense and corrosion-resistant film,which reduces the corrosion rate of the alloy.In addition,the crystal lattice is distorted due to high-energy ion implantation,which hinders the movement of dislocations and improves the surface hardness of the alloy.(2)By depositing Zn and Ti ions at different times on the surface of WE43 alloy,Zn and Ti films with different thicknesses can be prepared.XRD and XPS results show that the thin film layer is mainly composed of deposited elements and their oxides.It is observed by SEM that the deposition time has a great influence on the quality of the film.When the deposition time is 800 s,both the Zn film and the Ti film are dense,and there are fewer defects.The quality of the film is closely related to the corrosion resistance of the alloy.Polarization curve results show that the Zn film and Ti film deposited for 800 s have the lowest I_corr values,which are 34.8 and 2.9mA·cm^-2,respectively.At the same time,electrochemical impedance spectroscopy also gave consistent results.During the immersion corrosion process,cracks preferentially appear at the surface defects and form corrosion products around them.In addition,the HIT and EIT of WE43 alloy before and after deposition of Zn and Ti are very different,but the deposition time has little effect on the HIT and EIT values of the film,indicating that the film does not change the bonding mode of atoms as the thickness increases.