Evolution of microstructure and mechanical properties during annealing of heavily rolled AlCoCrFeNi2.1 eutectic high-entropy alloy

Changes in the microstructure and mechanical properties during annealing at 800 degrees C have been characterized in a 90% cold-rolled AlCoCrFeNi2.1 eutectic high-entropy alloy containing the FCC and B2 (ordered BCC) phases. In the as-rolled condition, the FCC phase is found to contain a high frequency of finely spaced deformation-induced boundaries, which provides a high driving force for recrystallization within this phase. Quantitative analysis of electron backscatter diffraction data from the annealed samples indicates that recrystallization progresses faster in the FCC phase than in B2 regions. Although recrystallization leads to substantial coarsening of the microstructure, the average recrystallized grain size remains in the submicron range even after 2 h at 800 degrees C. Tensile test data demonstrate that combinations of high yield strength and good ductility are obtained in partially recrystallized samples produced by annealing for 2.5-10 min. However, the work-hardening capacity of each annealed sample is lower than that of the cold-rolled sample. Furthermore, for the samples annealed for at least 5 min a yield drop is observed soon after the onset of plastic deformation. Analysis of the microstructure and mechanical behavior in several annealed AlCoCrFeNi2.1 samples indicates a clear correlation between the magnitude of the yield drop and the recrystallized fraction. The mechanical behavior of the AlCoCrFeNi2.1 alloy studied in this work is compared with that reported in previous publications.