Nanocrystallization, magnetic properties and bending ductility of antiferromagnetic Mn-doped FeSiBCuPC alloys induced by micro-compressive stress annealing

Abstract

Insufficient amorphous forming ability (AFA) and thermal instability have always been the bottleneck restricting the application of high Fe content iron-based nanocrystalline soft magnetic materials. In this work, the effects of micro-compressive stress annealing (MCSA) on microstructure, soft magnetic and mechanical properties of high Fe content FeSiBCuPCMn alloys were systematically investigated. We demonstrate that Mn doping effectively increases the AFA of the alloys and improves the thermal stability of the amorphous matrix. The change of coercivity (Hc) is closely related to the grain size, which depends on the Mn content and annealing process. It clearly shows that a small amount of Mn doping (≤3 at%) and MCSA can inhibit the excessive growth of α-Fe grains and reduce the grain size. Moreover, the low Mn-doped amorphous alloys exhibit good bending ductility even after annealing at appropriate conditions. After MCS-annealing at 420 °C for 10 min, the Mn-doped Fe85−xSi1.3B9P4Cu0.5C0.2Mnx (≤3 at%) nanocrystalline alloys exhibit comprehensive and excellent soft magnetic and mechanical properties, such as high Bs of 1.79–1.87 T, low Hc of 4.6–9.9 A/m and low Hv of 737–867.