Interface Strengthening of alpha-Mg/C14-Mg2Ca Eutectic Alloy

This study investigates the effect of the alpha/C14 interface on the creep strength of alpha-Mg/C14-Mg2Ca eutectic alloy at 473 K under a stress of 40 MPa. The alpha/C14 interface is composed of terraces and steps, with terraces parallel to the (1101)(alpha) pyramidal plane of the alpha-Mg lamellae and to the (1120)(C14) columnar plane of the C14-Mg2Ca lamellae. The creep curves of the alloy exhibit three stages: a normal transient creep stage, a minimum creep rate stage, and an accelerating stage. The minimum creep rate is proportional to the lamellar spacing, indicating that the alpha/C14 lamellar interface plays a creep-strengthening role. In the high-resolution transmission electron microscopy image captured of the specimen after the creep test, dislocations can be mainly seen within the soft alpha-Mg lamellae, and they are randomly distributed at the alpha/C14 interface. In contrast, dislocations are rarely introduced in the hard C14-Mg2Ca lamellae. It is deduced that the alpha/C14 interface presents a barrier to dislocation gliding within the alpha-Mg lamellae and does not help rearrange the dislocations.