Abstract:

The on-going energy crisis demands extensive research into new alternatives for enhancing the energy efficiency in electric motors. As a probable solution to this, soft magnetic materials (SMM) portray excellent properties with high saturation magnetisation (JS) and low coercivity (HC)[1]. SMMs possess the ability to cater to this need, as they can substantially increase the efficiency in electric motors by reducing the core losses. Although promising, the soft magnetic Fe-based amorphous metals need further research to overcome production challenges, as the need for high cooling rates to generate a significant fraction of the amorphous phase severely limits their production to thin ribbons resulting from rapid solidification processes such as melt spinning. Earlier work on additive manufacturing (AM) parameter optimization of an Fe-Si-B-based bulk metallic glass (BMG) has, however, shown promise for the fabrication of relatively large net-shape rotors [2].
In this work we carry out process optimization for producing an Fe-based metallic glass composition (Fe-Si-B-Cu-Nb) using the selective laser melting (SLM) process. Process optimization is highly complex, as printing conditions favoring high densities usually lead to low fractions of the amorphous phase. Here, exhaustive iterations on 2 major SLM printing parameters, namely, laser power (W), scan speed (mm/s),) are performed to produce simple geometry specimens. Next, the SLM parameters, the density of parts, the heat affected zone (HAZ) or meltpool morphologies, and the degree of amorphousness have been correlated with the magnetic properties. To achieve this, complementary structural characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) have been utilized in conjunction with image analysis tools. The magnetic behavior was subsequently characterized using a vibrating sample magnetometer (VSM). The outcome of this work will provide guidelines for the design of soft magnetic bulk metallic glass components with more complex geometries and improved energy efficiency.