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

Abstract

In tensile tests, α-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 α/C14 interface on the creep strength of α-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 α/C14 lamellar interface plays a creep-strengthening role. In high-resolution transmission electron microscope observations of the specimens after the creep test, a-dislocations appeared within the α-Mg lamellae and were randomly distributed on the α/C14 interface. It was deduced that the α/C14 interface presents a barrier to dislocation glide and does not annihilate and/or rearrange the dislocations caused by the creep test.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 85 (2021) 223–228.

Fig. 3 Plots of minimum creep rate vs. lamellar spacing for the α-Mg/C14–Mg₂Ca eutectic alloy, where the creep tests were carried out at 473 K under a stress of 40 MPa.