Microstructure and Physical Properties of Dual-Phase Soft Magnetic Fe-Co-Ti-Ge Alloys

Soft magnetic materials play a crucial role in determining the efficient operation of power electronics and electrical machines. Recently, compositionally complex alloys have shown to offer promising magnetic properties that can be engineered by composition and microstructure. In this work, we investigate the microstructures and physical properties of novel dual-phase Fe-Co-Ti-Ge alloys by introducing ferromagnetic Heusler-type phases into a disordered ferromagnetic matrix. The microstructure of three alloys is studied in the as-cast and homogenized state and is primarily composed of a Fe-Co BCC-A2 matrix phase and Fe-Co-Ti-Ge-based L21-ordered Heusler phases. A Ti-Ge-rich phase is observed to form in the Fe50Co20Ti10Ge20 (at%) alloy. The physical and magnetic properties of these alloys show a good combination of high electrical resistivity (202 – 252 µΩ‧cm), high Curie temperature (> 1000 K), moderate saturation magnetization (74 – 99 A‧m2/kg) and coercivity (390 – 1099 A/m). The phase arrangement, morphology and composition of the BCC-A2 and L21-Heusler phases are responsible for the observed differences in magnetic properties, which can be further tuned by tailoring the microstructure.