Microstructure and mechanical properties of CrMnFeCoNi high entropy alloy/Al composite with different reinforcement content

Abstract

The Al matrix composites with different HEA addition ranging from 5.2 wt. % to 19.8 wt. % were fabricated by rotation friction extrusion (RFE) process. The microstructure results revealed that the average grain size of the composites was pronouncedly reduced by 70.5–81.8 % than that of the RFE processed aluminum (RFEed Al), and abundant second phases were formed in the composites. The ultimate tensile strength (UTS) increased with the HEA content. Significantly, the UTS of the composite with 19.8 wt. % HEA content was 224.5 MPa, increased by 150.8 % compared with the RFEed Al, and the good uniform elongation of 16.7 % was maintained. The improvement in mechanical properties was caused by the grain refinement mechanism, Orowan strengthening, load transfer strengthening, and dislocation strengthening. The strain hardening ability of the composites was higher than that of the RFEed Al and increased with the HEA content, as a result of the formed second phases and the added HEA particles. However, the strain hardening rate of the composites decreased quickly because of the high dynamic recovery rate caused by fine grains, resulting in the low uniform elongation of the composites. The current research provides a fundamental understanding to develop HEA/Al composites.