Corrosion resistance and mechanical property of AZ31 magnesium alloy by N/Ti duplex ion implantation

Abstract

N/Ti duplex ion implantation was conducted on AZ31 magnesium alloy surface by metal vapor vacuum arc (MEVVA) ion source to improve its corrosion resistance and mechanical property. Auger electron spectrum (AES), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to characterize the elemental concentration-depth profiles and phase composition of the modified layer. The anti-corrosion performance of treated samples was evaluated using potentiodynamic polarization system and scanning electronic microscope (SEM). The surface hardness of ion implantation samples were measured by hardness tester. XRD analysis shows that Mg, MgO, Ti, TiO2 and TiN phases exist in the surface modification layer. AES result indicates that the surface layer thick is about 200nm; the ion dose and thickness of the implanted layer increase with the implantation voltage and treatment time. The depth profile of implanted N+Ti in AZ31 magnesium alloys is similar to Gauss distribution, and the maximum concentration up to 66at.%. The hardness of treated sample is 94.5HV0.01, increases by 50.7%. Compared with the bare substrate, the corrosion potential Ecorr of N/Ti duplex ion implantation coupon increases by 600mV, the corrosion current density icorr decreases by two orders of magnitude, and the polarization resistance increases by 66.4 times in a 0.56M NaCl solution. The corrosion resistance can be slightly improved by low implantation voltage. In addition, too high implantation voltage or too long treatment time have a negative influence on the corrosion resistance. The corrosion resistance of AZ31 magnesium alloy can be effectively improved by nitrogen and titanium duplex ion implantation.