Stress corrosion cracking in a Mg-Al-Ca alloyThursday (07.11.2019) 09:35 - 09:55 Part of:
The stress corrosion cracking behaviour in a Mg-4.7 wt.% Al-2.9 wt.% Ca magnesium alloy have been studied. The effects of distilled water on the corrosion behaviour was characterized by means of scanning electron microscopy (SEM) in combination with energy-dispersive X-Ray spectroscopy (EDX). The mechanical degradation by distilled water was evaluated by in-situ monitoring of tensile and bending tests. Here, the deformed microstructure was further examined under SEM and confocal laser scanning microscopy to reveal mutual interactions of mechanical slip bands and corrosive attack with the precipitated second phase and grain boundaries. The results indicate that the precipitated intermetallic phase is majorly the Laves phase (Mg, Al)2Ca, which acts cathodic relative to the matrix. The corrosion products do not effectively protect the matrix when exposing to distilled water. The continuous oxidation of the matrix leads to the formation of voluminous MgO and Mg(OH)2, however, which is quite brittle under mechanical loading and promotes further corrosion attack. The mechanisms of stress corrosion cracking in the investigated material were further discussed with the microstructure characterization and chemical composition analysis near the second phase and grain boundaries.