Abstract: AZ91-xCu (x=0, 0.5, 1, 2) alloy was prepared by vacuum melting method, and solid solution treated at 400 ℃ for 12 h. The phase, microstructure and corrosion properties of the alloy were studied by means of X-ray diffraction, scanning electron microscopy, immersion mass loss method and polarization curve test. The results show that the substrates of as-cast and solid solution treated AZ91-xCu alloys are mainly composed of α-Mg and β-Mg₁₇Al₁₂ phases, and the addition of Cu leads to Mg₂Cu and Cu₅Zn₈ phases precipitation in the substrates, among which a new phase Al₂Cu appears in the solid solution treated AZ91-2Cu alloy. During the solid solution treatment, the β-Mg₁₇Al₁₂ phase of the alloy is largely dissolved into the substrate and the grain boundary is obvious. The remaining second phase is mainly distributed at the grain boundary and a little disperses in the grain. The addition of Cu and the solution treatment both accelerate the corrosion rate of AZ91 alloy, among which the corrosion rate of the solution treated AZ91-2Cu alloy is the highest.

Key words: AZ91-xCu alloys, solid solution treatment, second phase, corrosion rate