Iron-rich layer introduced by SMAT and its effect on corrosion resistance and wear behavior of 2024 Al alloy

The nanocrystalline microstructure of the surface of 2024 Al alloy induced by surface mechanical attrition treatment (SMAT) was determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion behavior of 2024 Al alloy after SMAT was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). A pin-on-disk tribometer was used to determine the tribological properties of nanocrystalline layer under dry sliding conditions. The results demonstrated that the Al nanocrystalline layer with an average grain size of 55 nm, when treated for 30 min, was produced at the surface of Al alloy. However, a 5 μm thick surface layer containing Fe, the grain size of which was in nanometer scale, was also introduced into the top layer of Al nanocrystalline surface. The iron-rich layer led to the diminution of corrosion resistance of 2024 Al alloy, while the wear resistance was improved due to the beneficial combination of refined grains, increased hardness and lubrication effect of iron-rich layer.