Effects of micro-alloying Ag on microstructure, mechanical properties and corrosion behavior of extruded Mg-2Zn-0.2Ca-xAg alloys

Abstract

The present work investigates effects of micro-alloying Ag on the microstructure, mechanical properties and corrosion behavior of as-extruded Mg-2Zn-0.2Ca alloys. The addition of Ag, up to 0.5 wt%, induce limited difference on microstructural characteristics such as slightly coarser microstructures due to the enhanced dynamic recrystallization process and the presence of refined precipitates. The tensile properties of the alloy were not significantly changed by Ag addition, i.e., all the alloys exhibited exceptional elongation of ∼30%, moderate tensile yield strength and ultimate strength of ∼140 MPa and ∼240 MPa, respectively. The corrosion performance of the alloys was progressively deteriorated with increasing Ag content i.e., the corrosion rate increased from 0.40 ± 0.23 mm/y for Mg-2Zn-0.2Ca alloy to 3.27 ± 0.24 mm/y for the Mg-2Zn-0.2Ca-0.5Ag alloy. The compromised corrosion performance was attributed to a large electrode potential difference between the nobler Ca2Mg6Zn3 phase and the α-Mg matrix as well as a less protective corrosion film, by increasing Ag addition.