C and N doping in high-entropy alloys: A pathway to achieve desired strength-ductility synergy

Abstract High-entropy alloys (HEAs) have attracted great attention because they provide diversified possibilities for obtaining many exceptional properties. They are expected to serve as structural materials in the fields of industry, aerospace, biomedical science and so on. Therefore, it is desirable to simultaneously attain high strength and good ductility in those alloys. Interstitial alloying has been recognized as a powerful and economic approach to enhance mechanical properties for HEAs, and its effect mainly depends on the content of interstitial atoms, microstructures, and element distributions. In this review, recent progress on the interactions between interstitial atoms (i.e., Carbon (C)/Nitrogen (N)) and HEAs with various crystal structures together with the relationship between microstructures and bulk mechanical properties are summarized. The basic physical problems, including absorption, solubility and distribution of C and N atoms, as well as the influence of interstitial alloying on deformation mechanisms of HEAs, have been discussed. Finally, four models describing micromechanical behaviors in the interstitial HEAs are constructed, which is anticipated to guide the development of more advanced HEAs.