Enhancing strength via nano-lattice defects in La0.008Al0.08FeCoCrNiMn high-entropy alloy produced by rapid solidification, cold rolling and annealing

Multiple lattice defects play a crucial role in improving the mechanical properties of FeCoCrNiMn high entropy alloys (HEAs). In the present work, the strength and hardness of the La0.008Al0.08FeCoCrNiMn HEA were first increased and then decreased during the annealing process due to the competitive mechanism between the recrystallization softening and precipitated phase hardening. Especially, a superior room temperature ultimate tensile strength (1403 MPa) and a fracture strain (9.1%) have been obtained, which was treated by quenching in the liquid metal, cold rolling at room temperature, and annealing at 600 °C for 32 min. The characterizations and analysis indicate that the fundamental cause of the strengthening is attributed to the synergistic effects of nano-sized precipitated particles (mean size: 20.2 nm), dislocation cells, and nano-twins (∼10 nm in thickness) together with Lomer-Cottrell locks. Meanwhile, the effects of different lattice defects on strength contribution have been quantified.