Faceted Kurdjumov-Sachs interface-induced slip continuity in the eutectic high-entropy alloy, AlCoCrFeNi2.1

Recently, the eutectic high-entropy alloy (EHEA), AlCoCrFeNi2.1, can reach a good balance of strength and ductility. The dual-phase alloy exhibits a eutectic lamellar microstructure with large numbers of interfaces. However, the role of the interfaces in plastic deformation have not been revealed deeply. In the present work, the orientation relationship (OR) of the interfaces has been clarified as the Kurdjumov-Sachs (KS) interfaces presenting 111B2||110FCC and 110B2||111FCC independent of their morphologies. There exist three kinds of interfaces in the EHEA, namely, (321)B2||(112)FCC, (011¯)B2||(332¯)FCC, and (231¯)B2||(552)FCC. The dominating (321)B2||(112)FCC interface and the secondary (011¯)B2||(332¯)FCC interface are both non-slip planes and atomistic-scale faceted, facilitating the nucleation and slip transmission of the dislocations. The formation mechanism of the preferred interfaces is revealed using the atomistic geometrical analysis according to the criteria of the low interfacial energy based on the coincidence-site lattice (CSL) theory. In particular, the ductility of the dual-phase alloy originates from the KS interface-induced slip continuity across interfaces, which provides a high slip-transfer geometric factor. Moreover, the strengthening effect can be attributed to the interface resistance for the dislocation transmission due to the mismatches of the moduli and lattice parameters at the interfaces.