Lamellar Structure Stability of a Two-Phase α-Mg/C14–Mg<sub>2</sub>Ca Alloy

To evaluate the stability of α-Mg/C14–Mg2Ca lamellar microstructure, aging treatment was carried out for a Mg–14.8 mass% Ca near-eutectic alloy at 573–723 K 1–150 hours. The spacing microstructure obtained by eutectic transformation L → α-Mg + C14–Mg2Ca during solidification approximately 250 nm. High-resolution transmission electron microscopy observations show that α/C14 interface is composed terraces and steps, with parallel to (1101) pyramidal plane lamellae. stable in morphology temperatures below 573 K. In contrast, (λ) continuously increases increasing time (t) above K, increase λ can be described as λ2 − λ02 = kTt, where λ0 as-cast specimen, kT constant depending on temperature. activation energy coarsening evaluated 112 kJ/mol, which close inter-diffusion Mg. hardness region decreases λ, indicating acts an obstacle basal slip dislocations