Obtaining a strong and ductile Co-rich high entropy alloy via synergistic effect of pre-twinning and nanolamellar L12 precipitates

Abstract

Alloys with high strength and competent ductility are highly demanded for modern engineering applications but difficult to design and prepare. In this study, we design a Co-rich Co₃₅Cr₂₀Fe₂₀Ni₂₀Al₂Ti₃ HEA that exhibits excellent tensile properties, facilitated by unique microstructures, namely pre-twins and nanolamellar L1₂ precipitates, which are introduced via multistep deformation and annealing. Comprehensive microstructural characterization, carried out through electron back scattering diffraction and transmission electron microscopy, demonstrates that interactions among lattice dislocations, pre-twins and nanolamellar L1₂ precipitates raise the dislocations slip stress barrier and dislocation storage rate, gifting the HEA a high strength and ductility mechanical properties. The present study provides insight into the fabrication of ultra-strong and ductile HEAs by tuning the substructures.