Creep Properties of Mg–14Ca Cast Alloy with Al

Creep tests were carried out for the Mg-14.2mass% Ca-2.9 mass% Al alloy (hereafter referred to as Mg-14Ca-3Al alloy) at temperatures between 498-548 K to elucidate the effect of Al addition on creep properties for the binary Mg-14Ca alloy.The Mg-14Ca-3Al alloy exhibits a fine lamellar structure with -Mg and C14-Mg2Ca phase, together with a small amount of the primary -Mg phase.It was confirmed that Al preferentially substitutes to C14-Mg2Ca phase rather than -Mg phase.The minimum creep rate for the Mg-14Ca-3Al alloy is approximately one seventh of that for the binary Mg-14Ca alloy at 498 K.The stress exponent of minimum creep rate for the Mg-14Ca-3Al alloy, n, continuously decreases with increasing temperature and the activation energy for creep, Qc, decreases with increasing applied stress.The formation of coarse lamellae during creep is limited around colony-boundaries at a low temperature, while it is pronounced typically at high temperature and low stress conditions.The change in creep parameters, n and Qc, for the Mg-14Ca-3Al alloy results from the decreased creep strength driven by the formation of coarse lamellae during creep.The minimum creep rate and creep rupture life for the alloy follow the phenomenological Monkman-Grant relationship.