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.