Effect of Laves Phases on Creep Strength for a Mg-Al-Ca Alloy

The effect of Laves phases, C36-(Mg,Al)₂Ca and C15-Al₂Ca, on high-temperature creep strength was quantitatively investigated for the Mg-5.0Al-1.5Ca alloy produced by die-casting. The homogenization treatment at 750 K for 1 h was carried out to divorce the interconnected skeleton of C36 phase, and the aging treatment at 523 K for 1-1000 h was performed to precipitate the C15 phase within the α-Mg grains. The creep tests to evaluate the creep strength were conducted at 447 K and 70 MPa. When the C36 skeleton is divorced, the minimum creep rate dramatically increases by a factor of 330. The coarsening of the C15 phase within the α-Mg grains increases the creep rate by a factor of 2.6. It was identified that the creep strength of the Mg-5.0Al-1.5Ca alloy is predominantly ascribed to the interconnected skeleton of C36 phase rather than the precipitation strengthening of C15 phase.