A novel D022 precipitation-hardened Ni2.1CoCrFe0.5Nb0.2 high entropy alloy with outstanding tensile properties by additive manufacturing

To introduce D0(22) superlattice (noted as gamma '' phase) precipitation strengthening in additive manufacturing, a design strategy of combining the overall valence electron concentration with the calculation of phase diagrams is proposed, and Ni2.1CoCrFe0.5Nb0.2 HEA is designed. The wall-shaped samples were prepared by AM, and after solution at 1100 degrees C for 2 h and aging at 650 degrees C for 120 h, the gamma '' phase with volume of 14% causes yield strength increase by 727 MPa, the yield strength increased dramatically to similar to 1005 MPa, the ultimate strength increased dramatically to similar to 1240 MPa, the tensile elongation maintained at similar to 20%. The high strength results from the precipitation strengthening of the gamma '' phase, and the large ductility are primarily attributed to an evolution of multiple stacking fault structures. The present study will not only promote the development of high-performance HEAs by AM but also provides a pathway for achievement of AM technology industrial applications.

Automated summary

This study proposes a design strategy that combines the overall valence electron concentration with the calculation of phase diagrams to introduce precipitation strengthening of D0(22) superlattice (gamma'' phase) in additive manufacturing. By designing a Ni2.1CoCrFe0.5Nb0.2 high-entropy alloy and subjecting it to solution and aging treatments, the yield strength and ultimate strength dramatically increased, while maintaining a large tensile elongation. The high strength is attributed to the precipitation strengthening of the gamma'' phase, while the large ductility is primarily due to the evolution of multiple stacking fault structures. This research not only promotes the development of high-performance high-entropy alloys by additive manufacturing, but also provides a pathway for the industrial application of additive manufacturing technology.