Excellent strength-ductility synergy in oxide dispersion strengthened AlCrFeNi high-entropy composites by heterostructure strategy

Oxide dispersion strengthened (ODS) AlCrFeNi high-entropy composites were produced by different heterostructure strategies to achieve strength and ductility synergy. The effects of different reinforcement types, reinforcement contents and oxide-forming elements in the matrix on the microstructure and mechanical properties of ODS-AlCrFeNi composites were investigated. The results showed that in the composites with different reinforcement types (ternary ODS-CrFeNi, quaternary ODS-CoCrFeNi and quinary ODS-CoCrFeNiMn), spinodal decomposition is observed in the all reinforcements, resulting in the formation of ellipsoidal/cuboidal B2-structured NiAl-rich phase and BCC-structured FeCr phases. As the number of the principal elements in the reinforcing phase decreases, the spinodal decomposition size gradually decreases. In the composites with varying ODS-CrFeNi reinforcement contents (5 %, 10 %, 15 %, 20 %), the occurrence of spinodal decomposition is also observed in the reinforcement. The spinodal decomposition size in the composite with 15 % and 20 % reinforcement content is smaller than that with 5 % and 10 % content. It is noteworthy that the incorporation of oxide-forming elements of Zr and Ti or only Zr together with Y₂O₃ in to the matrix result in different reinforcement structures. The former is typical spinodal decomposition, whereas latter displays a gradient network structure comprising a FCC-structured FeNi phase and a BCC-structured Cr-rich phase. The superior strength-ductility synergy, a compressive strength and strain of 7690 MPa and 15.5 %, which are 2.7 and 2 times higher than those of the unreinforced reference alloy, respectively, is achieved. This is mainly contributed by the novel gradient network structure in the reinforcement.