Multi-property evaluation of low Cu content Fe-Cu magnetic alloys

Next generation magnetic materials used in high frequency rotating electrical machines, e.g., motors, require a good balance of magnetic, electrical and mechanical properties. Pure Fe has good magnetic properties but has insufficient resistivity and strength. Adding Cu to Fe can improve resistivity and strength. In this work, Fe-xCu (x = 1 to 4 wt %) alloys were studied. The Cu content was restricted to a maximum of 4 wt % to minimize detrimental effects to the magnetic properties. The mechanical properties were investigated using profilometry-based indentation plastometry (PIP) and micro tensile tests. A desirable doubling of yield strength and ultimate tensile strength was observed with increasing Cu content, from 317 to 801 MPa and 417 to ∼888 MPa respectively in tensile tests. Microhardness correspondingly increased from ∼225.7 to ∼368.2 HV. There was a three-fold increase in resistivity to ∼28 to 30 µm.cm, as compared to Fe, while M_s, H_c and T_c were in the range of 204 to 210.6 emu/g, 5.6 to 6.1 Oe and 758 to 762 °C, respectively. These alloys exhibit the desired good balance of magnetic, mechanical and electrical properties. Our results show that low Cu content Fe-Cu binary alloys are promising low-cost materials for next-generation electrical machines.