Microwave absorption of FeCoNiCrMn high-entropy alloys: An extended study on the synergistic effect of MgO content (0-5 wt.%) and annealing temperature

The development of high-performance microwave absorbing materials for extreme environments remains a significant challenge. In this work, the microwave absorption properties of a FeCoNiCrMn high-entropy alloy (HEA) were successfully modulated through an MgO doping strategy. A series of FeCoNiCrMn-based composites with MgO doping concentrations of 0, 1, 3, and 5   wt.% were fabricated, followed by annealing at 600 °C for 60   min in a nitrogen atmosphere. Electromagnetic characterization revealed that the doping level plays a critical role in determining the absorption performance. The composite with 3   wt.% MgO exhibited the optimal performance, achieving a minimum reflection loss ( RLₘᵢₙ ) of -55.02   dB and an effective absorption bandwidth ( EAB max ) of 4.4   GHz, while the sample with 1   wt.% MgO also demonstrated excellent absorption properties. Furthermore, the annealing temperature was confirmed to be another critical parameter, as the absorption properties of samples annealed at 500, 550, 650, and 700 ℃ exhibited markedly weaker absorption performance than those annealed at 600 °C. The optimal performance arises from the coupled effect of MgO doping and annealing at 600 °C. This processing window optimizes interfacial polarization and the defect/strain state of the HEA matrix, thereby achieving a favorable balance between impedance matching and attenuation. Beyond presenting a promising HEA-based absorber, this work elucidates the critical synergy between doping and thermal processing in tailoring electromagnetic properties. The understanding of this interplay ultimately provides new insights for designing high-performance microwave-absorbing materials.