Unraveling the Effect of Elastic Stress on the Destabilization Process of Ni–Sn Eutectic Lamellae at an Elevated Temperature

Beneficial from the fine lamellar structure, eutectic metallic alloys exhibit good strength-ductility synergy and are often used in high-temperature structural applications. However, such application usually exerts external stress on the material, which could destabilize the lamellar structure and degrade the mechanical properties. In order to unravel the effect of elastic stress on the destabilization process of lamellar structure, herein, we investigated the microstructural evolution of Ni–Sn eutectic lamellae under different elastic stresses at 1073 K. Meanwhile, a mathematical model was established to evaluate the destabilization process by taking both external stress and temperature into consideration. Both experimental results and the mathematical model showed that elastic stress could accelerate the destabilization of eutectic lamellae, and the destabilization time decreases with increasing the elastic stress. In general, the effect of elastic stress on the destabilization of the eutectic lamellae is twofold. In the early stage of destabilization, the elastic stress would generate different elastic energy density between trough and peak, which would cause diffusion of atoms from trough to peak and trigger the destabilization process. Subsequently, the elastic stress acts as a driving force for the destabilization process, with the assistance of interfacial energy. This work could provide guidance for the application of eutectic alloys.