Exceptional nanostructure stability and its origins in the CoCrNi-based precipitation-strengthened medium-entropy alloy

The thermal stability of second-phase nanoparticles plays a critical role in determining the applicability and durability of precipitation-hardened alloys for engineering applications at elevated temperatures. In this work, the temporal evolutions of coherent L1₂ nanoparticles were quantitatively evaluated in a CoCrNi-based medium-entropy alloy. Our experimental results demonstrated an extraordinarily sluggish coarsening of these nanoparticles as compared to most conventional superalloys. The underlying origins of such remarkable nanostructure stability were further analyzed based on the ripening theories, which could be ascribed to the combined effect of small interfacial energy and slow elemental diffusion.