Effect of purification treatment on corrosion resistance of Mg-Gd-Y-Zr alloy
(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 mm to 2.0 mm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/(m2·d) to 2.4 g/(m2·d) in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.
Key words: Mg-Gd-Y-Zr alloy; filtering purification; inclusion; corrosion rate; polarization curve; polarization resistance