Hot deformation in nanocrystalline Ndben Feben B backward extruded rings

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 Nd_30.5Fe_bal.Co_6.0Ga_0.6Al_0.2B_0.9 (wt%) is used as starting material. The effects of process variables, such as deformation temperature (T_d), 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 B_r and (BH)_max reach the optimum values at T_d=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.     

Pr2Fe14(C,B)/α-(Fe,Co)型纳米晶复合磁体的结构与磁性

研究了Pr_xFe_82-x-yTi_yCo₁₀B₄C₄ (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B_r基本不降低,x=10.5时合金的B_r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: B_r=9.6 kGs(1 Gs=10^-4 T),_iH_c =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     

龙虾Panulirus叶状幼体饵料的研究

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。     

中国龙虾亲虾培育试验

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     

温度对泥蚶胚胎发育、幼体生长发育及变态的影响

用广西防城港海区２～３龄增均体重１０克／只～１２克只的泥蚶作为新贝,对泥蚶胎发育、幼体生长发育及变态与温度的关系进行试验研究;试验温度为１９℃、２１℃、２３℃、２５℃、２７℃、２９℃、３１℃、３３℃。试验用水为沙滤海水,比重１．０１４～１．０２０,ｐＨ值８．０～８．２。结果表明,胚胎发育最适温度为２５℃～３１℃,由此温度带求得的胚胎发育温度系数Ｑ１０为２．０５。在高低极端温度下,胚胎发育畸形而死亡