Improve Microwave Absorption Strength and Corrosion Resistance of FeCoNi(AlSi)Cr _<i>x</i> High‐Entropy Alloys by Tuning Face‐Centered Cubic/Body‐Centered Cubic Phases

Multicomponent alloys with elevated configurational disorder, specifically FeCoNiAl 0.4 Si 0.6 Cr x (where x varies as 0, 0.1, 0.3, or 0.5), are synthesized using a planetary ball milling technique. The phase ratio of face‐centered cubic to body‐centered cubic (BCC) in high‐entropy alloys (HEAs) is modulated through precise control of the Cr content. The phase composition, morphology, static magnetic properties, electromagnetic performance, and corrosion resistance of HEAs are systematically investigated. The valence electron concentration (VEC) in FeCoNiAl 0.4 Si 0.6 Cr x HEAs decreases with increasing Cr content. Concurrently, the proportion of the BCC phase composition augments, which engenders atypical alterations in both static magnetic and electromagnetic properties. Additionally, the FeCoNiAl 0.4 Si 0.6 Cr 0.3 HEAs exhibit superior electromagnetic performance. In the C‐band spectrum, the reflection loss attains a value of –48.32 dB, with a corresponding thickness of 3.5 mm, and the effective absorption bandwidth is 4.96 GHz at a thickness of 1.5 mm. This investigation demonstrates that the crystal structure of FeCoNiAl 0.4 Si 0.6 HEAs can be tuned by strategic VEC design, resulting in superior electromagnetic wave absorption performance and improved corrosion resistance.