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采用了X射线衍射、扫描电镜和振动样品磁强计,研究了富稀土钕铁硼Nd_(10.5)Pr_(2.5)Fe_(80)Nb_1B_6合金真空感应熔炼、0.60~0.76 mm吸铸片的凝固过程和凝固择优取向特征。结果显示:0.76 mm吸铸片贴模面Nd_(10.5)Pr_(2.5)Fe_(80)Nb_1B_6因较高的冷却速度抑制α-Fe相的析出,过冷液体导致2∶14∶1相大量形核、沿热流方向等轴晶快速凝固,等轴晶组织具有垂直贴模面(006)磁织构,最后为富稀土相凝固;随着凝固界面的推进、冷却速度降低到一临界值以下,凝固机制发生改变,较低的冷却速度有利初生α-Fe相以树枝晶生长,随后2∶14∶1相在α-Fe相旁大量形核,成分过冷的液体有利2∶14∶1相以厚片状晶以[410]方向凝固,最后液体为富稀土相。0.60 mm吸铸片(Nd,Pr)2Fe14B从两侧贴模面形核以柱状晶向内部生长,最大长度超过吸铸片厚度一半,α-Fe相受到较大冷却速度的抑制,数量大幅度减少,0.60 mm吸铸片[006]磁取向进一步优化,剩磁提高73%,矫顽力提高到189.61 k A·m-1。
X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer were used to investigate the solidification process of Nd-rich (10.5) Pr_ (2.5) Fe_ (80) Nb_1B_6 alloy by vacuum induction melting and 0.60 ~ 0.76 mm suction castings And coagulation preferred orientation characteristics. The results show that Nd_ (10.5) Pr_ (2.5) Fe_ (80) Nb_1B_6 at 0.76 mm die cast surface inhibits the precipitation of α-Fe phase due to the higher cooling rate, and the supercooled liquid leads to a large amount of 2:14:1 phase The nuclei rapidly solidify along the equiaxed grains in the direction of heat flow. The equiaxed grains have perpendicular texture (006) magnetic texture and finally become rich in rare earths. With the advancement of the solidified interface, the cooling rate decreases below a critical value, The solidification mechanism changes, the lower the cooling rate is conducive to the growth of primary α-Fe dendrite growth, followed by 2:14:1 phase next to the α-Fe phase mass nucleation, the composition of the supercooled liquid favorable 2:14:1 phase Solidified in the form of slab-like crystals in the [410] direction, the final liquid is enriched with rare earths. 0.60 mm (Nd, Pr) 2Fe14B nucleated from both sides of the mold surface to columnar growth to the maximum length of the cast slab thickness of more than half of the α-Fe phase by a larger cooling rate of inhibition, the number of significant Reduced, 0.60 mm cast slabs [006] The magnetic orientation was further optimized with a remanence increase of 73% and a coercive force of 189.61 kA · m-1.