Abstract: Microstructure, phase composition and corrosion morphology of Mg-4Sm-3Gd-0.5Zr (mass fraction, %) alloy before and after solution and aging treatment were studied by means of optical microscope, X-ray diffractometer and scanning electron microscope, and the static weight loss experiment and electrochemical test were carried out in NaCl solution with mass fraction of 3.5%. The results show that the as-cast Mg-4Sm-3Gd-0.5Zr alloy is composed of α-Mg matrix and coarse network eutectic phases Mg₄₁Sm₅ and Mg₅Gd distributed along grain boundaries. After solution and aging treatment, the type of eutectic phases is not changed, but the network eutectic microstructure disappears, a large number of fine and dispersed second phases are precipitated in the grain and the grain boundaries are clearer. After solution treated at 525 ℃ for 8 h and aged at 225 ℃ for 8 h, the corrosion rate of the alloy decreases from 0.185 mg·cm^-2·h^-1 to 0.116 mg·cm^-2·h^-1, and the corrosion current density decreases from 1.599×10^-4 A·cm^-2 to 0.924×10^-4 A·cm^-2, at which the corrosion resistance is significantly improved.

Key words: Mg-4Sm-3Gd-0.5Zr alloy, solution and aging, microstructure, corrosion resistance