Revealing on metallurgical behavior of iron-rich Sm(Co0.65Fe0.26Cu0.07Zr0.02)7.8 sintered magnets

Abstract

The sintered magnets with the nominal composition of Sm(Co0.65Fe0.26Cu0.07Zr0.02)7.8 were prepared by standard metallurgical method. The evolution of phase transformation of the specimens during heat treatments was investigated in detail. After isothermal aging at 1103 K for 20 hrs and step cooling to 673 K and keeping for 10hrs, the remanence Br of the specimens almost keeps constant (∼11.5 kGs), while the intrinsic coercivity Hcj increases from 7.9 to 31.5 kOe. The maximum energy product of the final magnet is close to 32 MGOe. The phase is single phase with 1:7H structure in the specimen A only annealed at 1453 K for 4hrs. It is found that a cellular microstructure with a platelet Z-phase have appeared in the sample after the isothermal aging in 1103 K for 20h, which contain 2:17R, 2:7R and 5:19H phases. Furthermore, the 1:5H phase has appeared after the step cooling to 873 K, together with some 2:17R, 2:7R and 5:19H phases. Interestingly, it is found that the phase transformation has completed after the step cooling to 773 K. And the phase constitution in specimens is stable during the step cooling to 673 K.

High‐Remanence Fe‐Rich 2:17‐Type Sm–Co Sintered Magnets Mediated via Multiscale Microstructure

“…[ 8–13 ] However, B r tends to be constant when the Fe content is greater than 23 wt%, in contrast to the increase linearly of that before Fe contents reach 23 wt%, as illustrated in Figure a. [ 7,14–20 ]…”

“…Data are from refs. [7,14–20]. Insets show comparison of microstructure of Fe‐rich magnet before and after synergistic process optimization in this article.…”

“…[8][9][10][11][12][13] However, B r tends to be constant when the Fe content is greater than 23 wt%, in contrast to the increase linearly of that before Fe contents reach 23 wt%, as illustrated in Figure 1a. [7,[14][15][16][17][18][19][20] Remanence is a technical magnetic parameter, which is very sensitive to the preparation process and microstructure. A detailed summary of previous research literature shows that there may be three main factors to inhibit the improvement of remanence in Fe-rich 2:17-type Sm-Co sintered magnets.…”