Nd10.5Pr2.5Fe80Nb1B6合金吸铸片凝固过程研究  

Solidification Process of Suction-Cast Nd_(10.5)Pr_(2.5)Fe_(80)Nb_1B_6

作　　者：王艳[1] 张勇[1] 刘新才[1] 潘晶[1] 王红玉[1] 潘建峰[1] 董友仁[1] 王慧[1] 郑强[1] 刘进军[1] 

机构地区：[1]宁波大学材料科学与化学工程学院,宁波市新型功能材料及其制备科学重点实验室,浙江宁波315211

出　　处：《中国稀土学报》2016年第2期158-165,共8页Journal of the Chinese Society of Rare Earths

基　　金：国家自然科学基金项目(51174121和51274125);浙江省重点科技创新团队项目(2012R10016-08);宁波大学王宽诚幸福基金资助

摘　　要：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Nd10.5Pr2.5Fe80Nb1B6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Nd10.5Pr2.5Fe80Nb1B6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。The X-ray diffraction,scanning electron microscopy,vibrating sample magnetometer were used to study the solidification process,solidification preferential growth direction of the suction casting sheets of Nd10.5Pr2.5Fe80Nb1B6,with the thickness of 0. 60 ～ 0. 76 mm,prepared by vacuum induction melting and suction-casting. At the area near to the surface of the 0. 76 mm suction-cast sheet,the α-Fe phase precipitation from the melt was prevented for the higher cooling rate. The numerous nucleation crystal cores of the 2∶ 14∶ 1 phase were formed in the supercooling melt,and they solidified in the opposite direction of the heat flow so fast as to be in the equiaxed grains.But they were with the（ 006） magnetic texture. At last,the rich rare-earth phase solidified. As the advance of the solidification interface of the 2∶ 14∶ 1 phase,when the cooling rate was lower than a critical value,the solidification process of Nd10.5Pr2.5Fe80Nb1B6 was changed. The α-Fe dendrites were of the primary phase. And as the temperature of the melt decreased,the numerous nucleation crystal cores of 2 ∶ 14 ∶ 1 were formed on the surface of α-Fedendrites. After that the composition supercooling melt was favorable for the thick lamellae of 2∶ 14∶ 1 to solidify in the direction of [410],at last the rich-RE phase formed. But in the suction-cast sheet with thickness 0. 60 mm,（ Nd,Pr）2Fe14B columnar grains formed near the mold surface,and developed. The longest columnar was 325 μm,more than half of the suction-cast sheet. And the α-Fe dendrites were greatly constrained for the higher cooling rate than that in the 0. 76 mm sheet,the number of the dendrites much decreased. So the [006] magnetic orientation was improved,the residual magnetization increased 73% compared to that of 0. 76 mm sheet,and the coercive force reaches 189. 61 k A·m^-1.

关 键 词：富稀土钕铁硼合金 凝固过程 晶体择优生长方向 (006)磁织构 冷却速度 吸铸片 

分 类 号：TB332[一般工业技术—材料科学与工程]