Composite Modified Surface Structure And Corrosion Resistance Of Az91 Magnesium Alloy

In order to improve the wear and corrosion resistance of AZ91 magnesium alloy, N,Cr,Ti,Al single ion implantation, N+Cr,N+Ti,N+Al duplex ion implantation, solution and aging(T6) treatment and then N+Al duplex ion implantation are conducted on the magnesium alloy surface. XRD,SEM,EDAX,AES,electrochemical testing system,microhardness tester and friction and wear testing machine are used to analyze the surface microstructure and mechanical property. Effects of different treatment on surface microstructur,corrosion resistance and mechanical propertiy on AZ91 magnesium alloy are studied.XRD results show that the basic smple includeα-Mg andβ-Al12Mg17 phases. AlN phase is indicated after N ion implanted into basic sample except Mg and Al12Mg17 phases, the diffraction peak position and intensity of Mg and Al12Mg17 shifted obviously. After Al ion implanted Al enrichs on the surface make fl separated and reduce a diffraction peak, whileβphase is found in other position. Solid solution of Cr and Ti are found from XRD pattern on the surface of Cr and Ti single ion implantation, them affect the substrate Peak. N+Cr,N+Ti and N+Al duplex ions implanted samples include CrN,TiN,Ti2N,AlN except a-Mg andβ-Al12Mg17. T6 and single ion complex treatment have the similar phases with single ion implantation, but the diffraction peak position and intensity are different. T6+N+Al treatment sample includesα,β,AlN and MgAl2O4.SEM analysis for N+Cr duplex ion implanted display that grain and morphology of the surface are very clear, but the membrane structure is not observed, it illustrates implanted elements give a clear show of sputtering effects on the surface. EDAX analysis found a certain number of impantation elements are indicated in different location, its elements distribution and composition of surface microstructure are changed by implantation ions. AES for N+Al duplex ion implantation analysis indicates that 30nm Mg,Al,O compound and 130nm modification layer exist in the surface.The results of micro-hardness testing revealed that the micro-hardness of treated sample significantly increases, in particular the micro-hardness of N ion implanted sample have the most significant increase, the micro-hardness increases by 38.8% than untreated sample. The wear testing display that a wear resistant layer is found after ion implantation on substrate surface reduce friction coefficient, and wear life has been greatly improved. The lowest friction coefficient is 0.18, the highest wear life achieve as 15min.The results of corrosion polarization curves in the 3.5% NaCl saturated aqueous solution revealed that, the Ecor,Icorr and Rp are changed after implantation and complex treatment. In particular, the self-corrosion potetial of N+Ti duplex ion implanted sample significantly increases by 117mV. Compare with the untreated and T6 treatment samples, the polarization resistance of N+Al duplex ion implantation complex treatment increases by 21.7 times and 9.1 times. The current intensity decreases by one order of magnitude. Compared with the untreated sample, the corrosion degree of implantation sample and complex modification sample are lower, under the same corrosion conditions.