Refractory Compositionally Complex Alloys with Coarse-Grained and Fine-Grained Regions Towards Strength-Ductility Synergy

We demonstrate the feasibility of crafting single-phase solid solutions with exceptional ductility relative to most refractory compositionally complex alloys, using a computational thermodynamic approach, namely the difference in the Gibbs free energy between solid solution phases. Using this concept, non-equiatomic variants can readily be studied across a wide composition space. Furthermore, we deliberately manipulated its grain size and fabricated a heterogenous structure through conventional thermo-mechanical processing. Refractory compositionally complex alloys are promising candidates for high temperature structural applications but most are reported for poor ductility and negligible cold-workability at room temperature. Here, we will define what heterogenous structure is comprising of fine-grained regions results from inhibited grain growth, while coarse-grained are from grain growth within large deformation bands. A strengthening mechanism unique to heterogenous structure is verified through mechanical behavior and density analysis using electron backscatter diffraction. This gives rise to both high strength and high ductility in refractory compositionally complex alloys.