Strength, plasticity and coercivity tradeoff in soft magnetic high-entropy alloys by multiple coherent interfaces

Traditional strengthening of alloys involves dislocation, second phase and grain boundary, which could deteriorate plasticity and coercivity (Hc). In this work, multiple coherent interfaces are introduced in Fe26Co25Ni20Cu15Al13.1Ga0.9 (denoted HEA2) soft magnetic high-entropy alloy, by which tradeoff among strength, plasticity and coercivity has been achieved. The strength is elevated to 414.6 MPa by the synergistic enhancement of FCC/BCC dual-phase interface, L12 nanoprecipitates in FCC phase and B2 nanoprecipitates in BCC phase. The fully coherent multiple interfaces (FCC/BCC, FCC/L12 and BCC/B2) bestow the HEA2 alloy with excellent plasticity exceeding 200%. More importantly, the smaller size of L12 and B2 nanoprecipitates than domain wall width and the multiple coherent interfaces wouldn't hinder domain wall movement, leading to a low coercivity of 334 A/m. Whereas, heterogeneous ordered B2 precipitates with size exceeding the critical width (δw = 132 nm) impose obvious pinning effect on the domain wall movement. This study provides guidance for developing novel alloys with balanced mechanical and magnetic properties for advanced electrical application.