Corrosion behavior of 7050 and 7075 aluminum alloys processed by reactive additive manufacturing

Abstract

In this work, high-strength 7075 and 7050 aluminum alloys were processed by the laser powder bed fusion (LPBF) technique. Titanium and boron carbide particles were added to base 7050 and 7075 alloy feedstocks. These reacted in the melt to form inoculants in situ, resulting in a crack-free, refined, and textureless microstructure. X-ray diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectroscopy (EDS) techniques were used to characterize the process-induced microstructure of the alloys. Reactive Additive manufactured (RAM) alloys showed precipitation of various sub-micron to nanoscale phases such as Zn-Cu, Cu-Fe, Mg-Cu, Mg-Zn, and pure Zn. The corrosion response of RAM alloys was analyzed and compared with respective wrought alloys by various electrochemical measurements such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and atomic spectroelectrochemistry (ASEC) techniques. A reduction in corrosion resistance was observed in RAM alloys as compared to wrought counterparts due to thepresence of unreacted Ti and B4C particles and a higher cathodic activation attributed to the underlying microstructure. Time evolution surface imaging and post-corrosion microstructures were analyzed to support the understanding of underlying corrosion mechanisms.