Enhanced corrosion resistance of Mg alloy ZK60 after processing by integrated extrusion and equal channel angular pressing

It was demonstrated in this work that the corrosion rate of Mg alloy ZK60 can be reduced through the use of an integrated process of extrusion and equal channel angular pressing concomitant with increased strength. The improvement in corrosion resistance, as measured by electrochemical experiments and immersion tests in NaCl electrolytes, was correlated with both grain refinement and the redistribution of Zn and Zr solutes within the microstructure. These microstructural changes impacted the relative anodic and cathodic reaction kinetics sustained by the alloy in a unique manner, whereby structural and chemical variations dictated the anodic reaction rates in the former and the cathodic rates in the latter. The observed decrease in the corrosion rate, combined with improved mechanical properties for ZK60, represents a scenario where two properties that are nominally inversely correlated can be improved simultaneously, offering an insight into how Mg can be unique in terms of its processing-property relationships. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.