Tuning microstructure via cold deformation and annealing for superb mechanical properties in Al0.5CoFeCrNiSi0.25 dual-phase high-entropy alloys

Abstract

In the field of metal materials, deformation and annealing play an irreplaceable role in improving the microstructure and optimizing the properties. In this study, we prepared Al0.5CoFeCrNiSi0.25 dual-phase high-entropy alloys (DHEAs) by vacuum arc melting and investigated their microstructure evolution and mechanical properties at different rolling and annealing temperatures. The results showed that the volume ratio of the FCC phase remained largely unchanged with increasing annealing temperature, with only small recovery for 10% reduction alloy. In contrast, the volume fraction and recrystallization ratio of the FCC phase in a 40% reduction alloy increased, and its recrystallization rate was higher than that of the BCC phase. Annealing the alloys at 900 °C formed the FCC, BCC, σ, L12, and B2 phases. As the annealing temperature increased to 1100 °C, the lamellar structure was changed, and the L12 and σ phases dissolved, leading to the gradual increase in the spacing size and volume fraction of the FCC phase. Increasing the annealing temperature reduced the yield strength but enhanced the ductility of DHEAs. Annealing for 1 h at 900 °C after 40% cold rolling enhanced their strength to 1360.61 MPa due to the high dislocation density and presence of σ phases but led to poor ductility. Annealing for 1 h at 1100 °C after 40% cold rolling produced a good combination of tensile strength (∼1267.8 MPa) and ductility (uniform elongation of ∼34.4%). Such remarkable strength and ductility may be attributed to the increased volume fraction of the FCC phase and the dual-phase heterogeneous deformation induction strain hardening effect.