Tuning anisotropic grain structures in additively manufactured CoSm magnets by laser melting

• Applicant: Professorin Dr. Dagmar Goll
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516736439

(CoCuFeZr)17Sm2 is currently the most promising permanent magnet material for additive manufacturing using the laser powder bed (L-PBF) process. Due to its solidification processes and phase equilibria, magnetically advantageous microstructures are formed, which also allow the production of anisotropic magnets using L-PBF. The permanent magnet properties result from precipitation structures which are formed during annealing without the need for powder metallurgical processes or rapid solidification. So far, L-PBF of (CoCuFeZr)17Sm2 has achieved a coercive field of µ0Hc = 2.8 T, a remanence of Jr = 0.8 T and a maximum energy product of (BH)max = 109 kJ/m3 at room temperature. The additively manufactured magnets with partial texture exhibit a 24 % higher remanence than comparable isotropic sintered magnets. The aim of the project is to develop a material-physical understanding of the formation of crystallographically directed grain structures in additively manufactured CoSm magnets. The aim is to enable the targeted production of anisotropic CoSm magnets using L-PBF, which have magnetic properties (µ0Hc, Jr, (BH)max) comparable to those of anisotropic CoSm sintered magnets. For this purpose, knowledge of the CoSm material is combined with knowledge of the effects of the L-PBF process on texture formation achieved on other materials. According to scientific literature, the utilization of (1) targeted temperature gradients in the melt pool and (2) epitaxy via the use of an anisotropic building platform (substrate) as well as (3) solidification in a directed magnetic field are particularly promising. Furthermore, the alloy composition is expected to have a significant influence on the solidification behavior and texture formation. Methods of three-dimensional microstructure characterization as well as the characterization of the magnetic properties will be used to qualitatively and quantitatively record and evaluate the texture formation and the relevant influences. For this purpose, the solidification texture will be analyzed locally resolved by light and scanning electron microscopy as well as by electron backscatter diffraction and the solidification process will be reconstructed on this basis. In addition, the magnetic hysteresis is measured in the three spatial directions of the samples to obtain information on the global magnetic anisotropy. On the basis of this fundamental understanding, we will identify the specific parameters that can be used to produce highly textured CoSm magnets using L-PBF.

• DFG Programme: Research Grants