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Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt-spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6Al0.2B0.9 (wt%) is used as starting material. The effects of process variables, such as deformation temperature (Td), strain rate (ε) and height reduction (Δh%), on the magnetic properties of the rings are investigated. A scanning electron microscope (SEM) equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and (BH)max reach the optimum values at Td=800℃, ε =0.01 mm/s, and Δh% =70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fe14B nanograins along the easy growth a-axis. 相似文献
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研究了PrxFe82-x-yTiyCo10B4C4 (x=9—10.5;y=0, 2)纳米晶薄带的结构与磁性. 结果表明,所有薄带皆主要由2∶14∶1, 2∶17和α-(Fe, Co)三相组成. 对于y=0的合金,其内禀矫顽力随Pr含量x的增加而增加,剩磁随Pr含量x的增加而减小. 以Ti置换部分Fe (y=2),合金的磁性能得到显著提高,表现为:添加Ti后,合金的剩磁Br基本不降低,x=10.5时合金的Br值甚至有较明显的提高;同时添加Ti后,合金的内禀矫顽力及退磁曲线的方形度都明显改善. 当x=10.5,y=2时,合金薄带的磁性能达到最佳值为: Br=9.6 kGs(1 Gs=10-4 T),iHc =10.2 kOe(1 Oe=79.5775 A/m)和(BH)max=17.4 MGOe. 随着Pr含量的提高,合金中的硬磁相2 ∶14 ∶1的含量相对增加,内禀矫顽力提高;而Ti置换Fe抑制了软磁相α-(Fe, Co)在快淬和热处理过程中的优先长大,使合金中软磁相和硬磁相的晶粒尺寸及比例趋向最佳组合,交换耦合作用明显增强.
关键词:
纳米晶永磁材料
2Fe14(C')" href="#">Pr2Fe14(C
B)
Ti添加
交换耦合 相似文献
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先后采用扁藻Platymonassp.、骨条藻Skeletonemasp.、金藻Dicrateriasp.、丰年虫Artemiasalina幼体、藤壶Balanussp.幼体、轮虫Brachionussp.、蓝藻粉(Spirulina)、丰年虾片、金B.P.、微粒子、黑粒子、贻贝Mytilusedulis卵巢.组成12个组合饲养中国龙虾Panulirusstimpsoni、密毛龙虾P.penicillatus、黄斑龙虾P.polyphagus的叶状幼体。结果发现扁藻+金藻+丰年虫的体+贻贝卵巢组合喂养效果好.蓝藻粉+丰年虫幼体+贻贝卵巢组合和丰年虫幼体+贻贝卵巢组合喂养叶状幼体也可以,但效果比前面组合差。 相似文献
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在100 L水缸中进行中国龙虾[ Panulirusstim psoni(Holthuis)]亲虾培育试验。亲虾按2 雌1 雄放养, 充气, 投喂虾类、贝类、鱼类等活鲜饵料。结果表明, 中国龙虾嗜好活饵,也食鲜饵, 不食粤海牌对虾料, 最爱吃虾类。致死水温为11℃以下, 12℃~13℃冻僵, 14℃~15℃反应迟钝, 16℃~17℃恢复摄食, 18℃~30℃进行正常的生理活动, 31℃以上易患病死亡。繁殖季节为2 月~10 月。当水温升到18℃以上, 雌雄拥抱交配, 20℃以上开始产卵及抱卵, 26℃以上孵化出叶状幼体。胚胎发育适宜温度为23℃~30℃。共培育出6 尾雌虾产卵并孵化出叶状幼体。其中2 尾雌虾1 年繁殖3 次, 3 尾1 年繁殖2 次, 1 尾1 年繁殖1 次。病害是困扰亲虾培育的重要因素 相似文献
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