Improvement of microstructure and corrosion properties of AA7075 Al alloy by melt shearing process

In this study, the simultaneous effects of shear force and Sn&Bi addition to molten 7075 aluminum alloy (wt.%: 5.7 Zn, 2.35 Mg, 1.47 Cu, 0.2 Cr, 0.17 Mn, 0.15 Fe, 0.07Si, 0.01 Ni, bal. Al) on corrosion resistance and microstructure was investigated. Through the melt shearing method, a uniform and homogeneous distribution of alloying elements as well as cathodic and anodic intermetallic compounds is possible in the melt. The main cause of localized corrosion is deposition of cathodic intermetallic compounds especially at grain boundaries which leads to nucleation of pitting corrosion; so this method can reduce corrosion rate. The results of polarization tests and Scanning Electron Microscope (SEM) images show that the simultaneous effect of the melt shearing process and addition of small amount of Sn or Sn&Bi to this alloy will improve the microstructure and corrosion resistance. (C) 2020 Elsevier B.V. All rights reserved.