Kink bands-mediated overcoming of strength-ductility trade-off and enhancement of creep resistance in a Fe-Cr-Al alloy

Abstract

In this work, kink bands (KBs) were introduced in Fe-Cr-Al alloys to simultaneously overcome strength-ductility trade-off and enhance creep resistance. KBs-containing samples exhibit exceptional mechanical synergy at room temperature, achieving a yield strength of 950 MPa, an ultimate tensile strength of 1.06 GPa, a uniform elongation of 9.5%, and a total elongation of 11.6%. Results indicate that this enhancement originates from complementary strengthening mechanisms of KBs-induced hetero-grain refinement and hetero-deformation-induced (HDI) hardening. Moreover, KBs-mediated crack deflection and grain boundary delamination effects preserve ductility. At elevated temperature (400°C), KBs maintain functional efficacy through persistent Hall-Petch strengthening and sustained HDI hardening despite significant grain boundary weakening. The suppression of boundary delamination arises fundamentally from reduced strain hardening differentials between grain clusters with high-density KBs and low-density KBs, mitigating intergranular crack initiation and propagation from interfacial strain incompatibility. Remarkably, KB-containing alloys exhibit superior creep resistance at 400°C and 500 MPa compared to their homogeneous counterparts. Creep deformation is primarily governed by screw dislocation glide, which results in a very low creep rate (4.3651 × 10⁻⁹ s⁻¹) and negligible creep strain, outperforming other cladding materials.