The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing,immersion testing and SEM observation.The results indicated that the corrosion resistance of Mg-15Y sample gradually deteriorated with immersion time increasing,which was consistent with the observation of corrosion morphologies.The solid-solution treatment decreased the amounts of second phase Mg24Y5.The Ecorr and corrosion rate of as-cast samples were both lower than those of solid solution-treated samples,and both increased with increment of solid solution-treated time.The corrosion mechanism was proposed for the galvanic,pitting and filiform corrosion which varied with the immersion time and solid-solution treatment.
The influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25 Y alloy were uniform corrosion, and the corrosion morphologies of Mg-(2.5, 5, 8 and 15) were the pitting corrosion and the small range, deep depth localized corrosion.
