Effect of Lamellar Spacing on Creep Strength of alpha-Mg/C14-Mg2Ca Eutectic Alloy

摘要

In tensile tests, alpha-Mg/C14-Mg2Ca eutectic alloy with a lamellar structure is plastically deformed above 473 K but ruptures before yielding at temperatures below 423 K. 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 40 MPa stress. The creep curves of the alloy exhibited three stages: a normal transient creep stage, minimum creep-rate stage, and accelerating stage. The minimum creep rate was proportional to the lamellar spacing, indicating that the alpha/C14 lamellar interface plays a creep-strengthening role. In high-resolution transmission electron microscope observations of the specimens after the creep test, alpha-dislocations appeared within the alpha-Mg lamellae and were randomly distributed on the alpha/C14 interface. It was deduced that the alpha/C14 interface presents a barrier to dislocation glide and does not annihilate and/or rearrange the dislocations caused by the creep test.