| Mg-9Al-Zn and Mg-9Al-Zn-0.6Ce-xCa magnesium alloys were prepared by permanent mold casting.The microstructure and corrosion resistance of the alloy were observed by scanning electron microscope and energy dispersive spectroscopy,optical microscopy,kelvin probe and electrochemical experiments.The Mg-9Al-Zn-0.6Ce-1.2Ca alloy was treated by different power ultrasound.The effect of ultrasonic treatment power on the structure of Mg-9Al-Zn-0.6Ce-1.2Ca alloy was investigated.alloy was analyzed from the mechanism.The effect of ultrasonic treatment power on the corrosion resistance of Mg-9Al-Zn-0.6Ce-1.2Ca alloy was investigated.The main conclusions are demonstrated as follows:(1)After adding 0.6%Ce to Mg-9A1-Zn alloy,Ce reacted with Al to form Al2Ce phase,the morphology of precipitate phases changed from continuously network to discontinuous one.After further adding 0.3%Ca to Mg-9Al-Zn-0.6Ce,the Ca was dissolved in the ?-Mg17Al12 phase.When the Ca addition raised to 0.8%,Ca reacted with Al to form Al4Ca phase.When the Ca addition raised to 0.8%,the morphology of precipitate phases was continuously network.(2)In Mg-9Al-Zn-0.6Ce-1.2Ca alloy,the average grain size of a-Mg phase was refined by ultrasonic treatment,and the volume fraction of ?-Mg17Al12 phase was reduced by ultrasonic treatment.With the increase of ultrasonic processing power from 600W to 750W,the grain size of a-Mg first decreases and then increases,and the volume and the amount of ?-Mg17Al12 phase decreases continuously,and the morphology of ?-Mg17Al12 phase changes from continuous network to discontinuous network.(3)Among the five experimental alloys,Mg-9Al-Zn-0.6Ce-1.2Ca alloy has the best corrosion resistance.The corrosion resistance of Mg-9Al-Zn-0.6Ce-1.2Ca alloy is the best.The weight loss rate of Mg-9Al-Zn-0.6Ce-1.2Ca alloy after 24 hours immersion is 0.0164g/cm2,which is 65.96%lower than that of Mg-9Al-Zn alloy.The corrosion current density of Mg-9A1-Zn-0.6Ce-1.2Ca alloy is one order of magnitude lower than that of Mg-9Al-Zn-alloy.The corrosion resistance of the alloy first increases and then decreases with the increase of ultrasonic power,when Mg-9Al-Zn-0.6Ce-1.2Ca alloy was treated by ultrasound.The weight loss rate of the alloy treated by 650W ultrasonic treatment after 24 hours immersion is 0.0057g/cm2,which is 63.46%lower than that of the alloy without ultrasonic treatment.The corrosion current density of the alloy treated by 650W ultrasonic treatment is one order of magnitude lower than that of the alloy without ultrasonic treatment. |
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