Efficient carburization of high-entropy alloys from polyethylene microplastics using a green mechanochemical process to obtain excellent wave absorbing performance

•A new idea for beneficial recycling of polyethylene microplastics was provided;•An efficient and green carburizing process was developed by a mechanochemical method using polyethylene.•The impedance matching was significantly optimized by carburization treatment.•The carburized-FeCoNiMn HEAs exhibited excellent adaptability to harsh environments. Polyethylene as a major white pollutant has a significant negative impact on the environment and the human health. Beneficial recycling of polyethylene through mechanochemical processes not only can eliminate environmental hazards, but also enable some beneficial industrial applications. In this work, polyethylene was used as the raw materials of carburization of FeCoNiMn high-entropy alloys (HEAs) by a green mechanochemical method. The phase structure, magnetic properties, high-temperature oxidation resistance, corrosion resistance and electromagnetic-wave absorbing performance of the obtained carburized HEAs were investigated in detail. The carburized-FeCoNiMn HEAs exhibited excellent corrosion resistance, suggesting great application potential for use in harsh environments. Besides, the impedance matching was optimized and the electromagnetic-wave absorption bandwidth was expanded by this carburization process. Specifically, the reflection loss of C10 (FeCoNiMnC0.1) at 8.88 GHz reached −65.07 dB at a thickness of 2.79 mm, and both the C50 (FeCoNiMnC0.5) and C90 (FeCoNiMnC0.9) exhibited a maximum absorption bandwidth of 5.45 GHz. This work provides a new concept of utilizing common microplastic pollutants to achieve efficient carburization of HEAs by a green mechanochemical process.