Effect of twins on the corrosion behavior of Mg-5Y-7Gd-1Nd-0.5Zr Mg alloy

Deformation treatment is an efficient method to improve the mechanical properties of Mg alloys. However, twins inevitably arise during the deformation treatment due to the hexagonal closed-packed crystal structure of Mg. The role of twins in the corrosion behavior of Mg-5Y-7Gd-1Nd-0.5Zr (EW75) Mg alloy was studied by scanning electron microscopy (SEM) observations, scanning Kelvin probe force microscopy (SKPFM), zero-resistance ammeter (ZRA) measurements, scanning vibrating electrode technique (SVET), electrochemical tests and weight loss measurements. It is found that the micro-galvanic corrosion between twins and matrix plays the dual roles: accelerate the dissolution reaction of Mg substrate and promote the formation of surface film. The formation of compact surface film dominates the reactions in the EW75 alloy with twins. As a result, the twins in EW75 alloy can improve the corrosion resistance. (C) 2018 Elsevier B.V. All rights reserved.