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Abstract Alloy powders with dual-phase nanocrystal (NC) and nanoglass (NG) have received much attention due to its small coercive force and high permeability, but the preparation of dual-phase high entropy alloy powders (HEAPs) simultaneously with larger aspect ratio constitute a great difficulty in microwave absorbing domain. Here, a new concept has been devised to tune the crystallinity of microwave absorber by regulating the phase proportion of milling precursor. A combination technology containing melting, strip casting, and milling has been adopted to prepare a serious of FeCoNiSi x Al 0.4 HEAPs to verify its correctness. Selective phase transition occurs in dry-milling process, generating various unique microstructures - NCs, NGs, and NGs embedding in NC grain. Besides, BCC phase content of HEAPs can be controlled by the amount of added ethanol. A less coercive force, increasing from 14.05 Oe (C 0.1) to 23.43 Oe (C 0.5), and a large magnetic permeability, varying from 2.41 (C 0.5) to 2.80 (C 0.3) at 1 GHz, can be obtained. Highlights • The crystallinity of powders relate to FCC phase proportion of milling precursor. • The phase structure of nanocrystal alloy ribbons can be tuned by element content. • Co-existed phase transitions promote the formation of dual-phase microstructure. • The variety of crystallinity lead to the change of magnetic properties. [ABSTRACT FROM AUTHOR]