Quantifying the influence of secondary phases on corrosion in multicomponent Mg alloys using X-ray computed microtomography

The corrosion of Mg multicomponent alloys has a strong correlation with secondary phase, which usually acts as a cathode to promote the occurrence of galvanic corrosion due to its higher electrode potential than the Mg matrix. In this work, X-ray tomography (XCT) has been used to identify the key correlation between corrosion and secondary phases in both traditional multicomponent AZ91 Mg alloy and newly developed rare earth Mg alloys (Mg-10Gd-5Dy-0.2Zr). The changes of corrosion morphology of AZ91 alloy and Mg-10Gd-5Dy-0.2Zr alloy with the corrosion time have been observed in situ by 3D reconstruction technology. To quantitatively analyze the effects of different kinds of secondary phases on the corrosion in Mg alloys, the variations of the average number density, average equivalent diameter and average distance between secondary phases and corrosion pits have been studied.