Effect of Ho Content and Heat Treatment on the Corrosion Resistance of Mg- x Ho-3Sm-0.5Zr Alloy

The corrosion resistance of as-cast Mg- x Ho-3Sm-0.5Zr, solid solution and aged Mg-8Ho-3Sm-0.5Zr alloys was studied by electrochemical experiments, weight loss tests and microstructure analysis. The results showed that adding a proper amount of Ho to the as-cast alloy can refine the grain size. Furthermore, Ho can promote the precipitation of the Mg 41 Sm 5 phase and form a new Mg 24 Ho 5 phase. The Mg-8Ho-3Sm-0.5Zr alloy has the strongest corrosion resistance because of its uniform structure and the smallest grain size. Then, the Mg-8Ho-3Sm-0.5Zr alloy was heat treated. The results indicate that after solution treatment, the microstructure of the alloy is uniformly dispersed, and the second phase is dissolved in α -Mg, which improves the self-corrosion potential of the matrix. Its corrosion resistance is slightly better than that of the as-cast alloys. After aging treatment, a large number of second phases are uniformly dispersed to form a corrosion barrier, which further reduces the corrosion rate.