Structurally Complex Precipitates Enhance Strength‐Ductility Synergy in a Duplex Medium Entropy Alloy

ABSTRACT Chemically homogeneous intermetallic nanoprecipitates (INPs), despite their high strength, are intrinsically hard and brittle and often suffer from glide‐plane softening, which can strengthen alloys but severely degrade uniform elongation. This strength–ductility trade‐off is further exacerbated at cryogenic temperatures by the inherent brittleness of bcc‐based phases in precipitate‐strengthened fcc/bcc duplex alloys. Here we propose a strategy that overcomes these limitations through the design of structurally complex INPs, i.e., the ductile B2 multicomponent INPs (MINPs) assembled with dispersive nanocores and a chemical‐heterogeneity shell, in duplex fcc/bcc Fe ₅₈ Ni ₁₆ Cr ₁₆ Al ₁₀ (at%) medium‐entropy alloys (Fe‐MEAs). Within the bcc constituent, these coherent core–shell B2 MINPs serve the dual role of dislocation sources and obstacles, analogous to the ordinary incoherent B2 MINPs that trigger twinning‐induced plasticity in the fcc constituent, yet they are substantially more effective in load transfer for high yield strength and in self‐hardening for large uniform elongation. Critically, the core–shell nanostructure suppresses the glide‐plane softening typical of conventional INPs and promotes the activation of unusual ⟨111⟩ dislocation multiplication and interactions under cryogenic conditions. This work demonstrates a structural complexification strategy for designing self‐hardening MINPs, opening a pathway to ductile, high‐strength materials for advanced cryogenic structural applications.