Hierarchically activated deformation mechanisms to form ultra-fine grain microstructure in carbon containing FeMnCoCr twinning induced plasticity high entropy alloy

Nanotructural evolution and grain refinement leading to heterogeneous bimodal structure were investigated during thermomechanical processing in carbon-containing FeMnCoCr twinning induced plasticity (TWIP) high-entropy alloy (HEA). The homogenized single-phase face-centered cubic alloy with the stacking fault energy of 19.4 +/- 2 mJ m(-2) was cold rolled up to thickness reduction of 84 % and annealed at 850 degrees C. Planar slip with profuse nanoscale deformation twinning was the dominant deformation feature at low rolling reduction (32 %). The heterogeneous structure could be obtained through subdivision of microstructure, continuous dynamic recrystallization and static recrystallization described as follows: (i) Hierarchical mechanical twinning, (ii) Interaction of twin-matrix (T/M) lamellae with shear-bands and (iii) Continuous dynamic recrystallization (CDRX) within the strain-induced boundaries (SIBs), (iv) Subsequent static recrystallization of the region with twin-matrix (T/M) lamellae and shear-bands. The strength and ductility enhancement during deformation was attributed to the hierarchy of microstructural evolution consisting of TWIP and microband-induced plasticity (MBIP). The heterogeneous bimodal structure composed of ultra-fine grains and larger grains with an average grain size of 0.5 mu m and 3 mu m respectively was achieved by post-rolling (84 %) annealing at 850 degrees C. Favorable strength-ductility combination with the ultimate tensile strength of 840 MPa and elongation of similar to 88 % was achieved by formation of heterogeneous bimodal microstructure through thermomechanical processing.

Automated summary

In carbon-containing FeMnCoCr twinning induced plasticity (TWIP) high-entropy alloy (HEA), heterogeneous bimodal structure can be achieved through subdivision of microstructure, continuous dynamic recrystallization, and static recrystallization.