| Abstract:Sm2Co17 permanent magnets have attracted much attention due to their high magnetic properties, high curie temperature and excellent resistance to corrosion. In this paper, the effect of Fe, Lu and aging treatment on the microstructure and magnetic characteristics of Sm2Co17 permanent magnets have been investigated systemtically. The main study of this research includes:(1) The effect of Fe content on the microstructure and the magnetic characteristics of Sm(CobalFexCu0.08Zr0.06)7.4 alloys.a. Fe content have no effect on the phase structure of Sm(CobalFexCu0.08Zr0.06)7.4 alloys. The XRD patterns of the alloys show that the alloys were mainly conmprised of 2:17R phase as the constituent and 1:5H phase. However, detailed ananlysis indicating that there is more 2:17R phase in the high Fe content Sm(CobalFexCu0.08Zr0.06)7.4 alloy.b. The remanence of Sm(CobalFexCu0.08Zr0.06)7.4 alloys increased obviously from 10.8kG to 11.3kG with x increased from 0.125 to 0.2, respectively. Further increase of x resulted in the decrease of remanence. However, The coercivity decreased when x increased from 0.125 to 0.25,35kOe for x=0 and 19kOe for x=0.25.c. TEM micrograghs of the cellular microstructure indicats that the average cell size and the density of lamella phase are almost the same for the alloys with x=0 and x=0.175. The average cell size was 172.4nm and 177nm for x=0.125 and 0.175,respectively. The density of lamella was 0.034/nm and 0.033/nm for x=0.125 and 0.175.respectively. However, Fe content in the Sm(CobalFexCu0.08Zr0.06)7.4 alloys has a significantly effect on the element distribution of the cell boundary and the lamella phase. The uniformly distributed of Fe changed the domain wall energy of the Sm2Co17 phase and the SmCo5 phase resulted in low coercivity caused by weaken the domain wall pinning strength. On the other hand, Cu is enriched in the cell boundary phase and Zr is enriched in the lamella phase. High resolution TEM graghs indicates that these alloys are mainly consist of three phase:(1) 2:17R phase as the constitument phase; (2) 1:5H phase as the cell boundary phase; (3) 2:17H phase as the lamella phase.d. The temperature coffient of coercivity increases with the Fe content increased, 0.22%/℃ for x=0.125 and 0.302%/℃ for x=0.175 for, respectively. (2)Effect of Lu doped on the magnetic characteristics and microstructure of (Sm1-xLux)(Cobal Fe0.125Cu0.08Zr0.06)7.4 (x=0-0.2) alloys.a. XRD patterns shows that Lu doped has no effect on the dominating phase of (Sm1-xLux)(Cobal Fe0.125Cu0.08Zr0.06)7.4 (x=0-0.2) alloys, which consists of 2:17R phase and 1:5H phase.b. Magnetic properties measurement shows that the coercivity was significantly increased by Lu doped,29kOe for x=0 and 36.5kOe for x=0.2. However, the remanence decreased from 11.1kG to 10.6kG when x increased from 0 to 0.1, then increased from 10.6kG to 10.8kG for x=0.1 and 0.2, respectively.c. TEM micrograghs of (Sm1-xLux)(Cobal Fe0.125Cu0.08Zr0.06)7.4 (x=0-0.2) alloys indicates that the cell size was significantly refined by Lu doped. The cell size of the alloys decreased from 172.4nm to 102nm for x=0 and 0.2, respectively. However, the density of the lamella phase has no change with Lu doped.d. EDS line scan was used to identify the element distribution in the cell boundary phase and the lamella phase, indicating that the alloys with x=0 and 0.2 show almost the same element distribution, while Lu is uniformly distributed in both cell phase and the lamella phase. Cu, Sm were enriched in the cell boundary SmCo5 phase and Zr was enriched in the lamella phase.e. The temperature coffient of coercivity was found increased from 0.164%/℃ to 0.287%/℃ for x=0 and 0.2 alloy. Detailed analysis indicating that the temperature coffient increased with x increased. (3) Effect of aging treatment on the magnetic properties of (Sm0.9RE0.1)(Cobal = Er, Ce, Gd, Lu and Nd/Pr) permanent magnets.a. Various of rare earth element were doped to synthesis (Sm0.9RE0.1)(Cobal Fe0.125Cu0.08Zr0.06)7.4(RE= Er, Ce, Gd, Lu and Nd/Pr) alloys. The maximun (BH)max of 30.8MGOe was obtained for Ce and Gd doped alloys.b.The cooling time in the aging treatment has a significant effect on the magnetic properties of these alloys. The remanence decreased from 10.91kG to 10.74kG for the undoped alloy when the cooling time was shortened from 10h to 8h. Then the remanence increased to 10.87kG with the cooling time decreased to 6h. Additionally, the remanence of other 5 alloys increase with cooling time decreased.c. Effect of the isothermally aging time on the magnetic properties of these alloys was invesgated. The remanence increased significantly from 10.91kG to 11.22kG for the undoped alloy when the isothermally aging time was stortened from 10h to 6h. By the way, the (BH)max increased also from 28.14MGOe to 30MGOe. The maximum (BH)max of 30.8MGOe was obtained for the Ce and Gd doped alloy with the isothermally aging time of 6h and the cooling time of 6h. |
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