Densification and Magnetic Properties of Injection Molded Gas- and Water-Atomized Fe–Si Alloys and Effect of Fe-10.2 wt% P Addition

This study investigated the effect of the water and gas atomized Fe–Si powders on the densification behavior and consequential magnetic properties of the sintered soft magnetic alloys by metal injection molding. The water and gas atomized Fe–Si powders were used to fabricate the injection molded parts with the same solids loading of 58 vol% to analyze the inherent characteristics of each powder admixture. Dilatometry analysis was performed to understand the densification behavior of the water and gas atomized powders, and the master sintering curve model was developed to quantify the differences. The results showed that a significant amount of oxides in the water atomized powder reduced not only the densification but also the overall magnetic properties. The gas atomized sample exhibited the higher sintered density than the water atomized sample, and consequentially higher magnetic induction was obtained. The lower core loss, lower coercivity, and the higher permeability were also obtained from the gas atomized sample with the relatively low oxide level and large grain size. In addition, Fe-10.2 wt% P (Fe-17 at% P) powder was added to activate the liquid phase sintering, as a method to overcome the weakness of poor densification of the Fe–Si powders. Although both the water and gas atomized samples achieved near-full density with Fe-10.2 wt% P, the gas atomized sample yielded superior magnetic properties as compared with the water atomized sample.