Influence of solid-solution treatment on corrosion performance of cast AM50 magnesium alloy

It was investigated by quenching the AM50 magnesium alloy test samples in water after T4 treating (420°C) for 24 h. Then both kinds of the test bars were immersed in 3.5 wt.% NaCl saturation Mg (OH)₂ aqueous solution for 0, 24 and 72 h. Then tensile tests were taken. The microstructure of the samples was analyzed by scanning electronic microscope and X-ray diffraction. The results show that though solid-solution treatment improved the corrosion residual strength of the cast AM50 magnesium alloy for 24h, the deeper corrosion pits developed on the heat-treatment samples on 72h caused more drop of the strength compare to the untreated samples. The solid-solution treatment and the extreme depth theoretical of corrosion pits effect together to the corrosion residual strength.