Orientation-dependent micromechanical behaviours of FCC/B2 dualphase AlCoCrFeNi2.1 high entropy nanopillars studied by atomic simulations

HF Zhang and ZF He and MH Zhang and S Jiang and N Jia and YL Feng, MATERIALS TODAY COMMUNICATIONS, 48, 113648 (2025).

DOI: 10.1016/j.mtcomm.2025.113648

The AlCoCrFeNi high entropy alloy with FCC/B2 ultrafine lamellar heterostructure has attracted much attention due to its excellent strength and ductility. To reveal the orientation dependence of the mechanical behaviors for FCC and B2 phases in nanoscale, as well as the influence of FCC/B2 heterogeneous interface on the deformation mechanisms, uniaxial tensile deformation have been carried out using molecular dynamics simulations on FCC/ B2 single crystals with different orientations and bicrystals containing different heterogeneous interfaces. The results show that the mechanical behaviors of FCC and B2 single crystals exhibit significant orientation dependence. During plastic deformation, the fluctuation of stresses of FCC single crystals is more significant and the plastic deformation ability is better than B2 single crystals. The synergistic effect of various deformation systems such as dislocations, twinning, and stacking faults activated in FCC single crystals makes them showing good plastic deformation ability. The number of dislocations activated in B2 single crystal is relatively small. The amorphous deformation region formed in the B2 crystal under applied loading is more likely to lead to strain concentration, which makes the plastic deformation ability poor. The stresses of bicrystals at the elastic-plastic transition point depend on the constituents. Dislocations are more likely to nucleate at heterogeneous interfaces and slip towards the FCC phase. Heterogeneous interfaces fail to play a reinforcing role and instead tend to lead to the accumulation of defects, resulting in strain concentration and non-uniform deformation of the bicrystals. The research results enrich the plastic deformation theory of eutectic alloy at the nanoscale and provide theoretical basis for orientation design of alloys with heterostructures.

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