Process-microstructure-mechanical and physical property relationships in additively manufactured electrical steels.

C. Backes, M. Kahlert, M. Smaga, M. Vollmer, T. Beck, T. Niendorf

In the ongoing energy transformation process the commonly established electrical steel regains broader attention. Conventional electrical steel sheets are usually limited at max. 7 wt% Si due to the degradation of the rollability. However, raising the Si content enables to increase electrical resistivity and therefor also reducing eddy currents and enhancing global magnetic properties. Relieving this trade-off additive manufacturing (AM) can be of potential because the AM process is not limited to rollability properties. Furthermore, combinations of processing parameters theoretically allow producing desired microstructure respectively texture and resulting magnetic properties.

Based on the outlined, the aim of this work was the investigation and comparison of additively manufactured electrical steels containing 3 wt% and 9 wt% Si regarding process-microstructure relationships as well as relationships between microstructure and magnetic properties. Cubic and toroidal samples had been produced via selective laser melting technique. Modifications in process parameters had been conducted concerning a building platform temperature with 200°C and 800°C. The investigation of mechanical and microstructural properties obtained that both building platform temperature and Si content had direct influence on porosity, density, hardness, and grain size. Further performed electron backscattered diffraction (EBSD) investigations confirmed observations from optical micrographs and correlated with mechanical properties. In addition, EBSD measurements were used to evaluate different orientation patterns that occurred. Addressing the physical properties investigations of the magnetic domain structure (MDS) using Magneto Optical Kerr Effect microscopy were realized revealing correlations between MDS and crystallographic orientation in selected magnetic domains.

Acknowledgments:

Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - TRR 173/2 - 268565370 Spin+X (Project B08).

Constanze Backes (M.Sc.)