A super strong high entropy alloy with discontinuous precipitation and fine grains by additive manufacturing and thermomechanical treatment

Despite previous work on achieving strength and ductility synergy of face-centered-cubic (FCC) high entropy alloys (HEAs) by additive manufacturing and thermomechanical treatment, it still relied on grain refinement, limiting the improvement of the mechanical properties of the HEAs. In the present work, as a common thermomechanical processing technique, cold rolling was applied to additively manufactured (AMed) HEA to further attain fine grain and discontinuous precipitation (DP)-containing microstructures. The perpendicular relationship between the rolling direction and the inherent dislocation walls in AM enabled maximum deformation energy storage during rolling, thereby promoting recrystallization and concurrent DP nucleation. The combined effects of high grain boundary mobility and elemental micro-segregation facilitated the discontinuous L1₂ precipitated microstructure. The resulting specimen exhibited an excellent yield strength of 1430 MPa and a tensile strength of 1800 MPa with 16% ductility. This combined approach provides a new means to tailor the heterogeneous characteristics of both coherent precipitates and grains, which is traditionally not available using AM method alone.