Multi-heterostructures synthesized via subsequent alloying of Y or Al into Mg melt using a 3D interconnected FeCr–Mg composite formed through liquid metal dealloying

Hierarchical multi-heterostructures were synthesized via a subsequent alloying process using Mg₉₀Y₁₀ or Mg₉₀Al₁₀ melt, based on a 3D interconnected FeCr–Mg composite developed through liquid metal dealloying (LMD) in a pure Mg melt. During the first immersion in the LMD process, Ni selectively dissolved from a (Fe₈₀Cr₂₀)₅₀Ni₅₀ precursor into the pure Mg melt, resulting in the formation of a 3D interconnected FeCr–Mg composite. The subsequent alloying with Y or Al in Mg melt induced distinct microstructural evolutions and mechanical properties. Y did not react with the FeCr ligaments but instead incorporated a secondary plate-shaped Mg₂₅Y₄ intermetallic phase within the soft Mg region. In contrast, Al addition caused significant microstructural modifications, including the formation of a thick Al-alloyed layer at the solid ligament and an ordered B2 phase. Particularly, the Al alloying reaction within the ligament increased the volume fraction of the solid phase during the subsequent alloying process. Furthermore, the Al-alloyed layer acted as a heterogeneous nucleation site during solidification, leading to the formation of Mg nanograins with a fine lamellar β-Mg₁₇Al₁₂ phase. The 3D interconnected multi-heterostructures, FeCr–(Mg–Mg₂₅Y₄) and FeCr–(FeCrAl)–(Mg₉₀Al₁₀), exhibited distinct mechanical properties compared to the unimodal FeCr–Mg composite, demonstrating higher yield strength and ultimate tensile strength. These findings underscore the potential of hierarchical 3D interconnected multi-heterostructures for enhancing the mechanical performance of advanced composite materials through tailored alloying strategies.