Effect of Heterogeneous Lamellar Structure on Mechanical Properties and Electrochemical Corrosion Behavior of Al-Zn-Mg-C
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JMEPEG https://doi.org/10.1007/s11665-020-04933-4
Effect of Heterogeneous Lamellar Structure on Mechanical Properties and Electrochemical Corrosion Behavior of Al-Zn-Mg-Cu Alloy Subjected to High-Pressure Torsion Kemin Xue, Biao Huang, Siliang Yan, Guangshan Wu, and Ping Li (Submitted August 9, 2019; in revised form June 16, 2020) The heterogeneous lamellar structure composed of a mixture of coarse crystal layer and fine crystal layer can improve the mechanical properties and corrosion resistance of the metal. To obtain high-performance aluminum alloy with heterogeneous lamellar structure, high-pressure torsion experiments have been carried out at 360, 380 and 400 °C. The results of tensile test and electrochemical corrosion test show that the strength of the alloy increases from 682.46 to 781.03 MPa and the polarization resistance increases from 42.91 to 81.12 kX cm2 with the increase in deformation temperature. It can be inferred from optical microscopy and transmission electron microscope observations that the strength of the alloy increases with increasing temperature. This is because the geometrically necessary dislocations at the interface increase during the stretching process, which in turn increases the back stress. Moreover, the enhancement of chemical corrosion resistance can be attributed to the decreased volume fraction of grain boundaries, which results in an increase in the compactness of the passivation film in the corrosive environment. Keywords
back stress, corrosion resistance, heterogeneous lamellar structure, HPT
1. Introduction Uniting low density, high strength and excellent fatigue resistance, Al-Zn-Mg-Cu alloy is widely used in aerospace field and is considered as a promising high-strength nonferrous material to replace steel and iron (Ref 1, 2). Despite its wide range of applications, the best combination of strength, toughness and corrosion resistance is still not achieved. High content of alloying elements causes a large amount of the second phase to be formed in the alloys, which leads to a decrease in corrosion resistance. Current methods generally increase the corrosion resistance at the expense of strength (Ref 3-6). Gollapudi (Ref 7) derives relationships for corrosion current and grain size distribution by utilizing existing correlations between corrosion current and grain size. These relations suggest that for the same average grain size, a broader grain size distribution leads to increased corrosion resistance in a non-passivating environment. Peng et al. (Ref 8) put forward that the increase in Cu content of grain boundary precipitates (GBPs) is one reason for improving corrosion resistance. Many researchers have proposed ideas to improve corrosion resistance, but the strength of the alloy is affected (Ref 9-11). Kemin Xue, Biao Huang, Siliang Yan, Guangshan Wu, and Ping Li, School of Material Science and Engineering, Hefei university of Technology, Hefei 230009, PeopleÕs Republic of China. Contact e-mail: [email protected].
Journal of Materials Engineering and Performance
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