Microstructure, mechanical and soft magnetic properties of in-situ TiC reinforced Fe27.5Ni27.5Co45-based medium entropy composites

Abstract

The insufficient mechanical properties of conventional soft magnetic materials (SMMs) hinder their widespread applications, and unfortunately, traditional strengthening mechanisms could dramatically deteriorate their soft magnetic properties without adjusting the alloy composition. Here, we developed TiC/Fe27.5Ni27.5Co45 medium-entropy composites (MECs) possessing multi-scale microstructure consisting of ultrafine and micron-sized grains by introducing in-situ formed TiC nano particles during the spark plasma sintering (SPS) process. Compared with the precipitate-free Fe27.5Ni27.5Co45 medium-entropy alloy, TiC/Fe27.5Ni27.5Co45 MEC with ∼ 8.7 vol% TiC (noted as Ti5-MEC) demonstrated a significant improvement in compressive yield strength (from 459 MPa to 1114 MPa), attributing to the grain-boundary strengthening and dispersive precipitation strengthening, as well as hetero-deformation induced (HDI) strengthening. Meanwhile, the Ti5-MEC exhibits a high saturation magnetization (Ms) of 153.1 emu/g and a low coercivity (Hc) of ∼ 8.2 Oe, indicating excellent soft magnetic properties, primarily due to the multi-scale microstructure. Our work has demonstrated that engineering multi-scale microstructures in MECs is an effective strategy to achieve desirable combinations of soft magnetic and mechanical properties.