Enhancement in Corrosion Resistance and Hardness of AZ91D Magnesium Alloy by Carbon Ion Implantation

Abstract

To improve the mechanical and corrosion resistance of AZ91D magnesium alloy, carbon ion implantation technique has been carried out using 2 MV Pelletron accelerator on the polished magnesium alloy surface. Vickers hardness test, particle induced X-ray emission (PIXE) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and corrosion tests are employed to analyse the properties. Vickers hardness tests revealed the improvement in surface hardness which we infer is due to the enhancement in dislocation density, as a consequence of carbon ion implantation with varied dose from 1.26×10¹³ to 8.4×10¹⁴ ions-cm^-2. That is, the increase in hardness is directly related to the ion dose, variation in lattice parameters, crystallite size, and change in peak intensity, all due to the increase in ion fluence. The non-destructive elemental analysis, PIXE, gave the elemental profile before and after ion implantation. SEM results indicated that singly ionized carbon ion implantation has modified the surface of AZ91D Mg-alloy. XRD results showed that the unexposed and treated samples include ?-Mg and ?-Mg₁₇Al₁₂ phases. XRD results also revealed that after the carbon ion implantation the diffraction peak position and intensity of all the phases shifted. The corrosion tests were carried out using two methods, namely, weight loss method and electrochemical test. The results guided that for a higher dose of ion implantation, the corrosion resistance increased and loss of mass of exposed surface of specimens decreased, which reflect the enhancement of corrosion resistance.