Origin of magnetic anisotropy formation in the HDDR-process of Nd2Fe14B-based alloys

Crystallographic alignment in the recombination stage in d-HDDR process of Nd-Fe-B-Ga-Nb powders

“…Although the shape of lamellar cluster after the HD step was different, above microstructural change during DR step was similar even when P HD was 100 kPa. orientation between α-Fe and NdH 2 grains in the disproportionated stage was reported previously, [8][9][10][11][12][13][14] and from the present study, such an orientation relationship is found to be maintained even when the DR process is under progress. On the other hand, no relationship among recombined Nd 2 Fe 14 BH y grains as well as between Nd 2 Fe 14 BH y and α-Fe or NdH 2+x grains was observed at this stage.…”

“…There are some reports suggesting the possible role of Fe 2 B as a memory site in the induction of the anisotropy, 11,14,16 however in the present study, the detection of iron boride phase was difficult, particularly in the DR step, and the role of B is still unclear. Considering that the amount of Fe 2 B formed during the HDDR process is small, an adequate control of reaction speed that maintains the orientation relationship between α-Fe and NdH 2 seems rather important.…”

“…This type of texture is commonly known as a hydrogen disproportionated state of Nd-Fe-B-based magnet. [8][9][10][11][12] It is a slightly difficult for the samples to avoiding absorption of the remaining hydrogen in the chamber during the cooling process of sample retrieval. Thus, the amount of hydrogen in the NdH 2+x is changed before cooling from the value at high temperature to room temperature.…”

“…7 Along with efforts to obtain the higher degree of anisotropy, investigations of the mechanism that induces such a crystallographic alignment have been intensively performed to date. [7][8][9][10][11][12][13][14][15][16] Further, from the microstructural observation as well as the analysis of orientations of crystal grains, it is now recognized that the α-Fe and NdH 2 grains formed during the HD process tend to align with some type of crystallographic orientation. [8][9][10][11][12][13][14] Currently, there are several reports that describe the details of such an orientation observed at the state where the HD step was completed; however, not enough information is available on the alignment behavior during the DR process.…”

Zr site determination and origin of magnetic anisotropy in HDDR processed Nd2Fe14B-based magnets

“…However controversy exists about the roles of these additives for the evolution of magnetic anisotropy. Several possible explanations have been proposed to account for the origin of magnetic anisotropy (Buschow, 1994;Tomida et al, 1996Tomida et al, , 1997Harris, 1992).…”