A TWIP-TRIP quinary high-entropy alloy: Tuning phase stability and microstructure for enhanced mechanical properties

Abstract

To understand the relations among phase stability, microstructure and deformation behavior of a non-equiatomic quinary Fe40Mn10Co20Cr20Ni10 (at.%) high-entropy alloy (HEA) with both transformation- and twinning-induced plasticity (TRIP & TWIP) effects, we systematically investigated the microstructural changes under different processing conditions and the corresponding tensile properties. The HEA has a single face-centered cubic (FCC) structure after thermomechanical processing. Inclusions enriched with Mn are rarely presented due to the relatively low Mn content compared to that in the reference equiatomic HEA. The HEA shows higher yield strength (375 MPa), ultimate tensile strength (785 MPa) and total elongation (77.5%) compared to the reference equiatomic HEA (349 MPa, 657 MPa and 59.9%, respectively) at a similar grain size of ~4.5 μm, which was also accompanied by the simultaneous increase of lattice friction stress and Hall-Petch coefficient. Further, introducing non-recrystallized zones of ~8 vol% significantly increases the yield strength (589 MPa) and ultimate tensile strength (865 MPa), at a high elongation (69.1%). Multiple strengthening mechanisms were activated upon deformation, including dislocation slip, nano-twining, and phase transformation, which explains the rationale behand the excellent strength-ductility synergy. The work further broadens the window for achieving a wide spectrum of mechanical properties of HEAs by phase stability-oriented alloy design and microstructure tuning.