Improving Tensile Strength and Ductility of Medium-Entropy Alloy via Three Principles of Composition Design

Composition design is one of the significant methods to break the trade-off relation between strength and ductility of medium-/high-entropy alloys (M/HEAs). Herein, we introduced three fundamental principles for the composition design: high elastic modulus, low stacking-fault energy (SFE), and appropriate phase stability. Subsequently, based on the three principles of component design and the first-principles calculation results, we designed and investigated a non-equiatomic Ni28 MEA with a single-phase and uniform microstructure. The Ni28 MEA has great mechanical properties with yield strength of 329.5 MPa, tensile strength of 829.4 MPa, and uniform elongation of 56.9% at ambient temperature, respectively. The high ductility of Ni28 MEA may be attributed to the dynamically refined microstructure composed of hexagonal close-packed (HCP) lamellas and stacking faults (SFs), which provide extremely high work-hardening ability. This work demonstrates the feasibility of the three principles for composition design and can be extended to more M/HEAs in the future.