Vermicular Eutectic Multi-Principal Element Alloy with Exceptional Strength and Ductility.

Abstract

Eutectic multi-principal element alloys (EMPEAs), with multiple main elements in compositions and eutectic microstructures, are considered promising high-performance materials for structural applications. The microstructure of EMPEAs usually exhibits a mixture of soft and hard phases in straight rod-like or lamellar morphology, which contribute to a balanced synergy of strength and ductility. However, such conventional morphology may also constrain the possible space for further improving their mechanical properties, and the question proposed is whether the straight morphology can be kinked to unlock a new space for achieving better mechanical properties. Here an (AlCrFe₂)₆₅Ni₃₅ EMPEA featuring an unseen kinked vermicular eutectic microstructure is successfully prepared. This innovative microstructure imparts remarkably improved strength-ductility synergy to the EMPEA, which surpasses both its coarse-grained counterpart and typical EMPEAs with straight morphologies, indicating a pronounced strengthening of the vermicular eutectic microstructure. The phase-field simulation reveals the formation of such microstructure as the lack of crystallographic locking caused by the similar elastic modulus of the two eutectic phases. The findings not only expand the family of possible eutectic microstructures but also offer a pioneering paradigm for enhancing EMPEAs, paving the way for their application in high-performance structural materials.