微量CaO对AZ81镁合金显微组织和耐腐蚀性能的影响

Effect of the addition amount of CaO (0, 0.1% 0.5% and 0.9% (mass fraction) respectively) on the microstructure and corrosion resistance of AZ81 Mg-alloy was studied by means of scanning electron microscopy, XRD, static mass loss and electrochemical measurement. The results show that: when the CaO amount was 0.5%, the grains of the alloy are refined obviously; the alloy is mainly composed of -Mg matrix and Mg17Al12 phase and there are also new phases Al2Ca and Mg2Ca generated in the alloy; along with the increase amount of CaO addition the corrosion rate of AZ81 Mg-alloy in 3.5%NaCl solution increases firstly and then decreases, while the free corrosion potential rises firstly and then falls, in the contrast the free corrosion current density of the alloy reduces firstly and then rises; when the addition amount of CaO was 0.5% the free corrosion rate and corrosion current density of the alloy are the smallest and the corrosion potential is the highest, therefore, the alloy possesses the best corrosion resistance property.