The effect of extension twinning on the electrochemical corrosion properties of Mg–Y alloys

• {101¯2} extension twins form in a Mg–1 wt.% Y alloy with a true strain of 1%.
• Extension twins improves electrochemical corrosion properties of a Mg–1 wt.% Y alloy.
• {101¯2} twins vary pitting potential, film formation and charge transfer resistance.
• The reasons root in a preferential oxide layer and low twin boundary energy.

The effect of extension twinning formed during compression deformation on the corrosion properties of an Mg–1 wt.% Y alloy was investigated using electrochemical tests. The corrosion morphology evolution after immersion in 0.9 wt.% NaCl aqueous solutions for various times has been analyzed by scanning electron microscope. The electron back-scatter diffraction result shows the {101¯2} extension twins appear in the deformed Mg–1 wt.% Y alloy with a true strain of 1%. The extension twinning accelerates the formation of oxide film and increases charge transfer resistance, resulting in the improvement of corrosion properties. However, it hardly affects the occurrence of microcracks in grain boundaries. The main reasons root in a preferred formation of homogeneous oxide layer in twinning area and low twin boundary energy.