Enhancing the strength and ductility of a medium entropy alloy through non-basal slip activation

Chen, Z.*; Gong, W.   ; Harjo, S.   ; Kawasaki, Takuro   ; Chen, G.*; 14 of others*

Developing alloys with both ultrahigh strength and ductility remains a for- midable scientific challenge, primarily due to the inherent strength-ductility tradeoff. Here, we present an approach to enhance the ductility and strength of a medium-entropy alloy (MEA) featuring a fully recrystallized face-centered cubic/hexagonal close-packed dual-phase ultrafine-grained architecture. This is achieved by activating unusual non-basal slips in the ordered hexagonal close-packed superlattice nanoprecipitates, resulting in this MEA that exhibits remarkable uniform elongation () and ultrahigh yield strength () across a wide temperature range, particularly at cryogenic temperatures ( 2100 MPa, 15%). The non-basal slips in the secondary phase are activated at ultrahigh stress levels, which are compatible with the increased yield strength of the MEA attained through multiple strengthening mechanisms, including grain boundaries, lattice friction, and second-phase nanoprecipitates provided by the multi-principal elements of the entropy alloy. The deformation mechanism elucidated in this work not only leverages the significant strengthening and strain hardening effects of brittle nanoprecipitates but also enables the ductilization of the alloy through sequential non-basal slip during ongoing deformation.