Effects of Y2O3 on the microstructure evolution and electromagnetic interference shielding mechanism of soft magnetic FeCoSiMoNiBCu alloys by laser cladding

Laser cladding is one of the new techniques for additive manufacturing of metal alloy-based electromagnetic shielding materials. However, it is generally difficult to prepare alloys with ideal printability, soft magnetism and electromagnetic interference (EMI) shielding effectiveness (SE) using this technique. To improve the electromagnetic shielding performance of laser cladded Fe-Co based soft magnetic alloys, a new FeCoSiMoNiBCu alloy was prepared by laser multilayer cladding using metal powders added with different content of Y2O3. The results show that the FeCoSiMoNiBCu alloys prepared under optimized laser processing parameters exhibit excellent soft magnetism and electromagnetic shielding properties. The microstructure of the prepared alloys is mainly composed of α (bcc) phase, Fe2B, YFe10Mo2 and B6Co21Mo2 phases. The Y2O3 powder has played significant effects on the soft magnetism and electromagnetic shielding properties of the alloys. When added with 1.5 wt% Y2O3, the alloy samples exhibit the highest saturation magnetization (186.2 emu/g) together with a superior EMI shielding effectiveness of 95 dB at 23.5 GHz, which is a 25–58% improvement compared the alloy without adding Y2O3. The mechanisms for the improved EMI shielding performance of the laser cladded FeCoSiMoNiBCu alloys depend on a synergistic effect of enhanced dielectric loss and ohmic loss; specifically, the α-Fe mainly promotes the dielectric loss, while the ohmic loss is enhanced by a “fish-bone” shaped phase composed of α (bcc) phase, Fe2B, YFe10Mo2 and B6Co21Mo2. This study provides a new theoretical and technical guidance for the development of high-performance EMI shielding alloys using laser cladding technique.