偏晶合金凝固研究进展

偏晶类合金作为1类重要的工程实用合金，以其独特的组织和特殊的性能，被材料学界争相研究。本文概述了偏晶类合金在微重力环境、定向凝固、深过冷和急冷快速凝固4方面的最新凝固理论研究进展。并指出了今后的研究方向。     

Microstructure of peritectic Tb-Dy-Fe alloys after electromagnetic levitation melting

1　INTRODUCTIONTb Dy Fealloy ,asarareearth (RE)magneticfunctionalmaterial,isofsignificanttechnologicalin terests ,becauseofitsgiantmagnetostrictionatroomtemperatureaswellashighenergydensityandfastresponsevelocityatlowfrequency[1] .Wideapplica tionfieldshavebeenidentifiedsincethematerialhadbeenexploited[2 ] .Thecompetitiongrowthbetweentheperitecticphase— (Tb Dy)Fe2 (REFe2 )andtheprimiaryphase— (TbDy)Fe3(REFe3)existsinthesolidificationprocessingoftheperitecticTb Dy Feal loys ,which…     

Effect of sample radius on stabilityof electromagnetic levitation melting

Based on the power dissipating model of spherical sample in free convection gas medium and the expression of input power, the model of temperature calculation for electromagnetic levitation melting sample was established. Considering the limitation of levitation force and levitation sample temperature, the principle of stability levitation zone computation was determined. A spherical sample (ThDy)Fe2 under the protection of argon gas was examined, and the effect of radius of levitation sample and perturbation on the stable levitation zone was investigated.The results show that longitudinal perturbation and transverse perturbation can shorten the length of stable levitation zone and the range of levitation sample radius. By increasing the sample radius and weakening the perturbation the electromagnetic levitation melting stability of sample can be improved.     

过冷包晶合金的相选择分析

分析了过冷包晶铁基合金、铜基合金、稀土超导乳化物、稀土木磁化合物非平衡凝固过程中的相选择现象。根据对实验结果的分析，对过冷包晶合金凝固的相选择进行了分类。探讨了过冷包晶合金凝固今后的研究方向和应用前景。     

真空电磁悬浮测定（TbDy）Fe2合金高温热辐射系数

利用试样在悬浮状态时重力与悬浮力相等，从而得到悬浮感应器的高频电流，进而得到悬浮感应器输入试样的功率。利用悬浮试样在热平衡状态输入功率与能量耗散平衡，从而得到合金的高温热辐射系数。并且利用这种方法测得(TbDy)Fe2合金在T=1455℃的热辐射系数为0．524。     

电磁悬浮熔炼试样的最低温度计算分析

根据Clemente R A计算电磁悬浮熔炼最低温度的办法，导出存考虑辐射散热和保护性气体自然对流散热联合作用情况下，球形试样电磁恳浮熔炼最低温度的计算模型。利用该模犁计算了不考虑气体散热、氩气自然对流散热、氦气自然对流散热3种情况下电磁恳浮熔炼球形试样的最低温度范围。通过对比，发现对于冷却能力筹的氩气，温度计算时可以不考虑气体散热；而对于冷却能力较大的氦气，对于高密度、高电阻率、低辐射率试样只考虑辐射散热计算球形试样最低电磁悬浮熔炼温度可行；而对于低密度、低电阻率、高辐射率试样，则必须考虑氦气散热与辐射散热联合作用计算球形试样最低电磁悬浮熔炼温度。不存存外部强制冷却的情况下，高熔点、低电阻率、低密度、高辐射率的试样，保护性气体冷却能力较强，试样易于在重力环境下实现悬浮过冷；而低熔点、高电阻率、高密度、低辐射率的试样，保护性气体冷却能力较差，试样难以在重力环境下实现悬浮过冷。     

深过冷Ni-31.44%Pb偏晶合金快速凝固行为

采用熔融玻璃净化和循环过热相结合的方法研究了Ni-31．44％Pb偏晶合金宽过冷区间的凝固组织演化规律；从形核热力学和动力学两方面分析过冷熔体中稳定相(α)和亚稳相(L2)两相的竞争形核规律。研究结果表明：过冷Ni-31．44％Pb偏晶合金在快速凝固阶段本质上是以枝晶方式生长，首先形成α枝晶骨架，再辉重熔后分布于枝晶间的残余掖相按照正常凝固模式进行分相／偏晶等后续反应。     

磁流变体制备与应用研究

通过对磁流变体基本组成和特性的深入研究,分析了磁流变体与电流奕体的本质区别,介绍了近年磁流变体的研究进展和应用状况,并阐述了其发展方向。     

电磁悬浮熔炼（TbDy）Fe2合金的耦合生长

实现了(TbDy)Fe2合金的电磁悬浮熔炼。采用红外测温、过程摄像、LECO图像分析仪、扫描电镜(SEM)以及电子探针等手段对(TbDy)Fe2合金在悬浮熔炼情况下的凝固特性、组织形成机理进行了分析研究。接近包晶成分该合金通过悬浮熔炼，熔体过热和快淬，凝固组织为基体相REFe2相，大量棒状REFe3相，富集于棒状REFe3相周围的大量富稀土相和少量存在于基体REFe2相中的富稀土相。这种现象的形成可以解释为该实验条件下，合金发生非平衡凝固，导致包晶REFe2相和初生REFe3相的耦合生长。包晶耦合生长和达到共晶反应温度所发生的共晶反应造成了这一现象。     

Vacuum Electromagnetic Levitation Melting and Undercooling of Peritectic Terfenol-D

For the first time, the undercooling of a magnetostrictive material-a near peritectic Tb0.27TDy0.73Fe1.90 alloy was realized by vacuum electromagnetic levitation melting and 60 K undercooling was obtained. There is one recaleseence be-havior during sol;difieation of the undercooled melt, which can attribute to the priority precipitation of REFe2 phase instead of REFe3 phase, due to preferential nucleation and higher crystal growth rate of REFe2 phase and the suppression of peri-tectic reaction. According to the crystal structural characteristic of REFe2 and REFe3, REFe2 is a Laves phase intermetal-lics with MgCu2 type structure, which has similar polytetrahedral structure wltn short range ordered structure in under-cooled melt and has lower potential barrier for nucleation than that of REFe3, which lead to the preferential nucleation of REFe2 phase directly from the undercooled melt. Also, the similarity of structures between REFe2 phase and undereooled melt leads to higher crystal growth rate of REFe2 phase than that of REFe3.