Creep Properties of a Binary Mg-14Ca Hypoeutectic Alloy*1

The binary Mg - 14Ca (mass % ) hypoeutectic alloy exhibits a fi ne lamellar structure of alpha-Mg and C14 (Mg 2 Ca) phases with the lamellar spacing of 0.9 mu m, together with a small amount of the primary alpha-Mg phase. Tensile creep tests were conducted for the alloy at temperatures between 473 - 523 K and stresses between 30 - 50 MPa. The overall creep rate vs. time in a log - log diagram for the alloy shows a downward curvature from stress application until creep rupture. A well-de fi ned steady-state is barely evident. The decrease in the creep rate during the transient stage is emphasized at lower temperatures and lower stresses. The coarse lamellar structure with the lamellar spacing between 1.5 - 2.5 mu m is evident at colony boundaries during the accelerating creep stage. It is found that the stress exponent of the minimum creep rate, n , is 7, and the activation energy for creep, Q c , is 146 kJ / mol. The value of Q c is close to that for the lattice self-di ff usion of magnesium (136 kJ / mol). It is deduced that the creep for the alloy is controlled by dislocation climb. [doi:10.2320 / matertrans.MT-M2024042]