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 ÿ–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 ÿ–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.