Microstructure‑Dependent Phase Transformations Under High‑Pressure Laser Heating in Additively Manufactured AlCrFe 2 Ni 2

Additive manufacturing (AM) produces microstructures the behavior of which under extreme conditions remains largely unexplored in chemically complex alloys. Here, we investigate the high‐pressure and high‐temperature response of an AM AlCrFe 2 Ni 2 alloy fabricated at two scan speeds: a high scan speed (900 mm/min), yielding a BCC/B2‐dominated microstructure, and a low scan speed (64 mm/min), producing a lamellar FCC + BCC/B2 eutectic. In situ synchrotron X‐ray diffraction reveals that both alloys undergo a pressure‐induced BCC/B2 → HCP transformation at ~13–19 GPa, demonstrating that the transition is governed by the intrinsic instability of the BCC/B2 lattice and is largely independent of phase fraction and microstructural morphology. Upon laser heating at high pressure, the HCP phase is not retained; instead, both alloys recover a cubic assemblage containing BCC/B2 together with more pronounced FCC reflections. The recovery of cubic phases occurs at a lower temperature in the low‐scan‐speed condition, consistent with its higher interphase‐boundary density and shorter diffusion pathways. The convergence of distinct AM microstructures toward a common high‐temperature cubic state establishes AM AlCrFe 2 Ni 2 as a model platform for disentangling lattice instability, hierarchical chemical partitioning, and diffusion‐driven phase selection in chemically complex alloys under extreme conditions.