Temperature-Driven Compositional, Morphological, and Crystallographic Evolution of FeCoNiMnCr High-Entropy Alloy Nanoparticles via Flash Joule Heating

High-entropy alloys (HEAs), characterized by their multiprincipal elemental compositions and unique core effects (high entropy, severe lattice distortion, sluggish diffusion, and cocktail effects), exhibit exceptional mechanical, catalytic, and functional properties. However, the extreme compositional diversity of HEAs poses significant challenges in achieving tailored materials for targeted applications. Herein, we report a flash Joule heating (FJH)-driven ultrafast synthesis strategy for the controllable fabrication of FeCoNiMnCr HEA nanoparticles (NPs) through a temperature-dependent phase evolution. Systematic modulation of FJH-induced thermal regimes (1300–2000 °C) reveals a critical temperature–composition–structure correlation: phase segregation dominates, yielding irregular Cr NPs, polyhedral MnCr NPs, and spherical FeCoNi NPs with distinct crystallinity at 1300 °C; heterostructured Cr/FeCoNi NPs emerge alongside metastable MnCr polyhedrons at 1600 °C; homogeneous FeCoNiMnCr HEA NPs form; and crystalline-to-amorphous transition occurs at 2000 °C or even higher. Multipulse FJH experiments further demonstrate the ability to decorate NPs with secondary phases (e.g., Cu heterocrystals), enabling performance customization. This work establishes FJH as a versatile platform for rapid HEA synthesis, offering fundamental insights into nonequilibrium thermodynamics and a pathway toward application-specific nanomaterial design.