Microstructure and properties of TiC/Fe24Ni24Co24Mn18 high-entropy composite with exceptionally low coercivity

Abstract

It is challenging to achieve good combinations of excellent mechanical properties and low coercivity (≤200 A/m) in typical soft magnetic alloys. In this work, TiC/Fe24Ni24Co24Mn18 high-entropy composite (HEC) prepared by mechanical alloying (MA) and spark plasma sintering (SPS) was produced to achieve good combinations of strength-ductility synergy and low coercivity. After MA, the TiC/Fe24Ni24Co24Mn18 HEC powders were composed of a main face-centered cubic (fcc) phase and some body-centered cubic (bcc) phase. Following SPS, the bulk TiC/Fe24Ni24Co24Mn18 HEC consisted of a fcc phase with nanosized TiC. In detail, the HEC showed multilevel heterogeneous microstructure, i.e., ultra-fine fcc grains (∼0.38 µm), micron-sized fcc grains (∼1.49 µm), and uniform dispersion of the in-situ formed TiC nanoparticles (∼98 nm) in ultra-fine fcc grains. The bulk TiC/Fe24Ni24Co24Mn18 HEC exhibits a high tensile yield strength of ∼1167 MPa and an exceptionally low coercivity of ∼100.5 A/m, suggesting an outstanding combinations of mechanical and magnetic properties. Compared with previously reported Fe-Co alloys or high entropy alloys (HEAs), the TiC/Fe24Ni24Co24Mn18 HEC shows a significantly enhanced yield strength while maintaining a relatively low coercivity, primarily resulting from the heterogeneous microstructure caused by the in-situ formed TiC.