Al–Sm and Al–Ca phases thermal stability effect on mechanical properties of Mg–3Al–2Ca–2Sm alloy

Abstract

The Al–Sm and Al–Ca phases thermal stability effect on mechanical properties of Mg–3Al–2Ca–2Sm alloy was studied. When the isothermal treatment temperature is 200°C and 300°C, the second phase formed in as-cast Mg–3Al–2Ca–2Sm alloy does not change significantly. The Al₂Ca and Mg₂Ca precipitated phases were precipitated during isothermal treatment. The alloy exhibits favourable tensile strength, elongation and fracture toughness. By increasing the isothermal treatment temperature to 400°C or even higher, the second phase began to decompose, except for the original particle Al₂Sm phase. The acicular Al₁₁Sm₃ phase breaks down into the particle Al₂Sm phase. Furthermore, the fish-bone Al₂Ca phase and lamellar (Mg, Al)₂Ca phase decompose into particle Al₂Ca phase. The mechanical properties and fracture toughness of the alloy decrease gradually.