Enhanced strength-ductility synergy in L12-strengthened high-entropy alloys via precipitation-induced matrix thermodynamic tailoring

초록

In this study, we investigated the mechanical behavior of a Co29Cr19Fe19Ni24Al4Ti4 high-entropy alloy (HEA) containing coherent (Co,Ni)3(Al,Ti)-type L12 nanoprecipitates. The formation of these nanoprecipitates contributed to significant order strengthening and enhanced work-hardening capability by promoting the refinement of planar slip bands. Furthermore, the precipitation-induced thermodynamic evolution of the matrix reduced its stacking fault energy (SFE), which facilitated the formation of stacking fault (SF) networks and Lomer-Cottrell (L-C) locks. These deformation substructures acted as additional barriers to dislocation motion, thereby improving strain hardening and delaying the onset of necking. As a result, an excellent balance between strength and ductility was achieved, with a yield strength of 760 MPa, a tensile strength of 1195 MPa, and a uniform elongation of 31 %. This study demonstrates that thermodynamic tailoring of the matrix via precipitation plays a pivotal role in enhancing the strength-ductility synergy, providing valuable insights for the design of high-performance structural HEAs.

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