Two distinct roles of Al2Sm and Al11Sm3 phases on the corrosion behavior of the magnesium alloy Mg-5Sm-xAl

The roles of Al₁₁Sm₃ and Al₂Sm phases on microstructure evolution, mechanical properties and corrosion behavior of the Mg-5Sm-xAl system was investigated. The results showed that adding Al to Mg–5Sm binary alloy brought two Al–Sm phases, Al₁₁Sm₃ and Al₂Sm, which had two distinct roles regarding the microstructure evolution, mechanical properties and corrosion behavior of the Mg-Sm-Al alloy. Al₁₁Sm₃ produced a strong galvanic couple with the Mg matrix, and significantly accelerated the corrosion. The Al₂Sm particles promoted heterogeneous nucleation and refined the grains, which increased the tensile strength and ductility. Both types of Al–Sm particles provided strengthening effect for the alloy. With higher Al contents, Al₂Sm formed an Al oxide protective surface layer and increased corrosion resistance.