Iron-cobalt-vanadium alloys can be processed to have excellent soft magnetic properties for use in high performance power generation applications such as the rotors and stators of aircraft integrated power units. These soft magnetic properties are, however, developed at the expense of mechanical strength and toughness. Small additions of niobium are reported to increase the strength of these Fe-Co-V alloys. This study evaluates the effects of heat treatment on the mechanical and magnetic properties of heavily cold work strip of a 48 wt.% iron-48 wt.% cobalt-2 wt.% vanadium alloy with a 0.3 wt.% addition of niobium. For heat treatments between 640 and 740°C for 1 hour the tensile and yield strengths and ductility of the alloy were all found to be superior to a similar alloy found in the literature without the addition of Nb and processed in a similar manner. Magnetic permeability, remnant induction, saturation induction, coercivity and core loss were only slightly degraded at all annealing temperatures when compared with the non-niobium containing alloy. All properties were shown to depend primarily on degree of recrystallization of the sample, which was found to fully recrystallize between 720 and 740 °C for 1 hour anneals. No significant change in measured properties were found when annealing time was increased to 2 hours. Full recrystallization was observed for samples annealed for as short of times as 10 minutes at 800 °C. / Master of Science

The FeCo-V alloy, commercially referred to as Hiperco, is known for its great soft magnetic properties. However, the high cost of production has limited the usage of this alloy to small-scale applications, where the small volume and high magnetic performance are critical. Additive manufacturing (AM) has the potential to solve the production problems that exist in Hiperco manufacturing. The present research has focused on selective laser melting (SLM) based AM processing of Hiperco. The goal was to perform a detailed examination of SLM processed Hiperco and determine how the process parameters affect the microstructure, mechanical and magnetic properties. While a systematic set of SLM process parameters were employed, the results indicate that the energy density was quite similar for this set of process parameters, resulting in similar properties. Overall, the saturation magnetization (Ms) values were very good, but the coercivity (Hc) values were very high, in the case of all as SLM processed conditions. Additionally, a large variation in porosity was observed in the as SLM processed samples, as a function of process parameters. Interestingly, long-term heat-treatments of these samples in an Ar+H2 atmosphere resulted in substantial decreases in the Hc values. These results are presented and discussed.

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Additive manufacturing (AM) procedures involving the fusion of metal powders or wires tend to produce textured columnar grains, which can have positive effects on the magnetic performance of Fe-Si electrical steels in soft magnetic applications. This work focuses on understanding the impact of energy density (fluence) evolution of grain morphology and texture in Fe-3.8wt%Si and Fe-6wt%Si alloys produced by fusion-based AM. The results show that the development of texture in these alloys is promising for transformers and motor core applications. The desired texture observed in these alloys is obtained in one step unlike conventional manufacturing techniques. The alloys with higher energy fluence exhibited columnar grains with preferential growth orientation along <001> along the build axis, while those with lower energy fluences showed growth orientation in <111> direction. Further, the presence of ordered B2, D03 phases observed in AM processed Fe-6wt%Si improved the overall magnetic performance of these alloys. Additionally, due to relatively high saturation magnetization and sustainability at high operating temperatures, Fe-Co-2V (Hiperco) is an attractive alternative for soft magnetic applications. In this study, Fe-Co-2V alloy is successfully manufactured using fusion based AM techniques and was found to exhibit equiaxed grains in the AM processed conditions. The microstructure was found to have a significant influence on the magnetic properties, leading to intriguing microstructure-property connections. This study will cover these links between microstructure and properties as well as how energy density (fluence) affects the microstructure of the two potential Fe-Si and Fe-Co-2V soft magnetic systems.