Ehancement of Strength-Ductility Trade-Off in Al ₅Fe ₂₅Cr ₂₅Ni _42.5Ti _2.5 High Entropy Alloy Through Annealing Twins

Abstract

High entropy alloys (HEAs) with single face-centered cubic (FCC) phase structure can provide excellent ductility, and microstructures such as twins and dislocations can be incorporated into the matrix to improve the strength of the alloy. Here, we designed a single FCC phase Al5Fe25Cr25Ni42.5Ti2.5 HEA with low stacking fault energy, and calculated the melting point (Tm) of the alloy by CALPHAD method to design the recrystallization annealing temperature. Compared with homogenized HEA, the yield strength of the alloy after cold rolling and recrystallization annealing is significantly increased. Both homogenized and recrystallized HEAs have three-stage tensile work hardening behavior. The CR-900 HEA grains annealed at 900 °C have higher dislocation density, high strength but some plasticity is lost. CR-1000 HEA annealed at 1000 °C almost completed complete recrystallization, with high density annealing twins in the grains, achieving a reasonable combination of high strength (792 MPa) and good ductility (62 %). Phase-field crystal (PFC) method was used to elucidate the underlying mechanism of the evolution of high-density annealing twins and independent dislocations during continuous loading. Our work provides a feasible method for designing strength-plastic equilibrium HEAs with different microstructures.

Keywords: High entropy alloys, twins, dislocations, cold rolling, recrystallization annealing