Effect of Y addition on microstructure and corrosion behavior of extruded Mg-Zn-Nd-Zr alloy

In this study, the effect of Y addition (0, 0.5, 1 and 2 wt%) on microstructure and corrosion properties of Mg-6Zn-0.5Zr-1Nd (wt%) alloy was investigated. The alloys were produced by low-pressure die casting method and extruded at 300 degrees C and 400 degrees C after homogenization treatment at 400 degrees C for 24 h. The results showed that the as-cast microstructure of the alloy with no Y addition consisted of alpha-Mg, Mg-Zn binary and Mg-Zn-Nd ternary phases. With increasing Y additions, the average grain size showed a substantial decrease and two kinds of ternary Mg-Zn-Y ternary phases, designated as I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2) were formed. Homogenization treatment resulted in a partial dissolution of second phase particles. Extrusion process gave rise to a remarkable grain refinement due to the DRX mechanism. The extruded alloys with no Y addition exhibited poor corrosion resistance due to the strong micro galvanic coupling effect. Y additions up to 1 wt% improved the corrosion resistance due to the formation of finer grains, fine and uniform distribution of second phase particles and more stable oxide film. (c) 2020 Published by Elsevier B.V. on behalf of Chongqing University.