from the conferences organized by TANGER Ltd. provisional website
The microstructure of initial Nd-Fe-B alloy has the substantial effect on the processing and the hysteretic properties of sintered Nd-Fe-B-based magnets. This work is aimed at the structural characterization of the strip-cast Nd-Fe-B alloy, which will be used as the matrix alloy for the preparation of magnets with variable set of functional parameters via the application of REM hydrides or hydrogenated REM compounds added to the powder mixture and using processes of grain boundary diffusion and grain boundary structuring. The microstructure, phase composition and distribution of Nd in the structural components of the strip-cast alloy were investigated by SEM/EDX, DTA and XRD methods. The nucleation region in the contact area between the cooling wheel and melt and radially grown Nd2Fe14B dendritic structure was observed. Individual dendrite arms are characterized by different crystal orientations and a thickness of 2 to 5 µm. In the interdendritic regions, the R-rich phase with a variable ratio of Nd/Fe is present. In this region, the NdFe4B4 compound was also identified as the minority phase. The X-ray elemental map showed the increased boron content in this phase. Major diffraction peaks in the XRD patterns could be indexed to either Nd2Fe14B or Nd-based phases. According to DTA data obtaining upon heating, the first peak is recorded in the temperature range of 693 to 731 °C which is probably related to the decomposition of NdFe4B4 phase. Other peak in a range of from 980 to 1061 °C is related to the melting of Nd-rich phases.Keywords: Nd-Fe-B alloy, strip casting, permanent magnet, microstructure, magnetic properties.