Tailoring of soft magnetic and tensile properties of Fe-Co-Ni-Al-Ti high entropy alloy by co-manipulating of recrystallization and coherent nanoprecipitation

Rapid development of flexible electronic devices poses a big challenge for soft magnetic materials (SMMs), which are required to not only possess low coercivity and high saturation magnetization, but also have high strength and ductility. Recently, a state-of-art strategy, nanoprecipitate engineering in ferromagnetic high-entropy alloys (HEAs), has been utilized to exploit strong and ductile SMMs. Unfortunately, these advances have encountered the limits of high cost due to the alloying of expensive solute atoms and relatively lower magnetization than the commercial ones. Moreover, the potential magnetic interaction between nanoprecipitates and matrix phase has not been fully understood due to the lack of technological characterization at the nano-scale. Herein, through co-manipulating of the recrystallization and nanoprecipitation behaviors, we have achieved a desirable balance between soft magnetic and mechanical properties in an original and low-cost FeCoNiAl0.12Ti0.12 HEA. Particularly, the optimized alloy showcases high saturation magnetization of 130 emu/g, low coercivity of 165 A/m, high tensile strength of 1118 MPa and good ductility of 12.6%. Further microstructural and Lorentz transmission electron microscopy (L-TEM) characterization have directly decrypted the nanoprecipitate-induced pinning effect for the motion of ferromagnetic domain walls, like that for the slip of dislocation. Our work may provide a microstructural basis for developing novel magnetic materials.