【作者】 龚维幂；

【导师】 于荣海；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 博士

【摘要】 本文研究了Zr含量、时效工艺等对Sm(Co,Fe,Cu,Zr)z合金中成分分布、组织、磁畴及磁性能的影响;通过调整z值、降低Fe含量、提高Cu含量、优化Zr含量设计了低矫顽力温度系数特征的Sm(CobalFe0.08-0.10Cu0.08-0.10Zr0.025)7.4-7.6合金;在此基础上采用吸铸法较大幅度提高了合金的室温磁性能,发展了一种具有优良高温磁性能的2:17型SmCo永磁合金。本文还在具有较高非晶形成能力的Y(Fe,Co)B共晶合金基础上,采用吸铸法实现了块体合金中纳米级层状周期结构的可控制备,并对其晶态、周期尺寸及磁性能成功进行了调控。采用电弧熔炼、吸铸、快淬法制备了Sm(CobalFe0.08-0.10Cu0.08-0.10Zr0.025)7.4-7.6合金的纽扣锭、吸铸合金及薄带试样,研究发现铜模吸铸法制备的尺寸为?6mm的Sm(CobalFe0.08Cu0.10Zr0.025)7.45合金性能稳定且室温下矫顽力达到16.47kOe;分析认为?6合金磁性能的改善与吸铸造成的晶粒细化、取向度增强及两相晶格错配度增加等因素有关。该成分的?6合金在温度升高到500℃以上时矫顽力才开始较快下降, 600℃时矫顽力仍能保持室温水平的70%,其高温磁性能优于目前报道的结果。在此基础上进一步进行了重稀土元素取代试验,Ho元素取代的(Sm0.5Ho0.5)(CobalFe0.10Cu0.08Zr0.025)7.55合金具有优良的室温磁性能,其纽扣锭合金室温矫顽力超过12kOe;250℃以上其相对矫顽力水平低于未取代的样品,但温度高于300℃后其饱和磁化强度则明显高于不含Ho的试样;针对不同的具体应用可对Ho元素的取代比例加以进一步优化。采用铜模吸铸法制备了?2～?9及截面尺寸为2×10的Y6(FeCo)72B22合金,合金具有软磁特性。研究发现,合金?2试样几乎完全为非晶态,随着冷却速度的降低,基体上开始析出有序相并最终形成纳米级层状结构,层状结构的周期随冷速的继续降低而逐渐增大,周期尺寸从?2.5试样中约40nm增加到?9试样中的约400nm。XRD、SAED和EDX分析认为层状结构中的两相分别为(Fe,Co)2B和富Y的αFe相。根据双相纳米晶的耦合作用,控制两相的组成可望在大范围内实现对磁性能的调控。尝试用Nd取代部分Y元素并且在外磁场下吸铸制备了?2合金,初步结果表明其矫顽力和剩磁比相对于纽扣锭合金均有数量级的提高,分别达到1.1kOe和0.3,为新型复合磁性合金的研发提供了新思路。更多还原

【Abstract】 The effects of Zr content and heat treatment on the distribution of alloy elements, magnetic domain and magnetic properties in Sm(Co, Fe, Cu, Zr)z alloy have been investigated. A new magnetic alloy with a low temperature coefficient of intrinsic coercivity (Hci) was designed by adjusting the value of z, lowering the content of Fe, increasing the content of Cu and optimizing Zr content. In addition, by using suction casting method, the Hci of this alloy at room temperature was improved considerably. On the basis of the optimization of component and the improving of fabrication process, an excellent 2:17 type SmCo permanent magnetic alloy was developed for high temperature up to 550~600℃. The Y(Fe, Co)B alloy with nano-layered structure was prepared by suction casting method. The controlled preparation of the nano-layered structure with different sizes could be achieved by changing the solicitation process. The hard magnetic property was achieved in this alloy replacing part of the Y by Nd element.The ingot, rod and ribbon of Sm(CobalFe0.08-0.10Cu0.08-0.10Zr0.02-0.03)7.5~7.6 alloy were prepared by arc-melting, suction casting and melt quenching methods, respectively. Results show that magnetic property of the fast-cooling alloy rod is remarkably enhanced and is much higher than that of the ingot and ribbon samples. The fast-cooling alloy rod with size of ?6 shows the most stable property and its Hci reach 16.47kOe at room temperature in Sm(CobalFe0.08Cu0.10Zr0.025)7.45 alloy. The Hci of ?6 sample does not show an evident decline until 500℃and its remains 70% of the value at room temperature when temperature was increased to 600℃, which is better than the results reported in the literatures. The critical temperatures at which the Hci of sample start to decrease obviously in ingot and ribbon with the same composition, are ~450℃. The more excellent magnetic property at room temperature of ?6 sample than that of the ingot and ribbon maybe due to grain refinement, change in the lattice parameters and misfits of 2:17 phase and 1:5 phase caused by suction casting. The substitution of Sm by the heavy rare-earth elements has been also investigated. (Sm0.5Ho0.5)(CobalFe0.10Cu0.08Zr0.025)7.55 ingot sample shows an excellent magnetic property and its Hci can exceed 12 kOe at room temperature. Its Hci is less than that of the sample without Ho element when the temperature exceeds 250℃. But its saturation magnetization (Ms) is much more than that of the sample without Ho element with the temperature above 300℃.The Y6(FeCo)72B22 alloy samples with the diameter of ?2mm ~ ?9mm and size of 2×10mm were prepared by suction casting method, which shows soft magnetic properties. The sample with size of ?2 is almost amorphous. With the increasing of sample size, in other words, the decreasing of the cooling rate, some nano-scale phases start to precipitate in the amorphous matrix and eventually forming the two phases nano-layered structure. It has been found that with lowering of cooling rate, the period of nano-layered structure increases from 40 to 400 nm in ?2.5 and ?9 alloys, respectively. The EDX result shows that the concentration of Fe and Y elements are enrichment regarding their own layers over each other. The presence of Co element does not show any significant change in both layers. XRD and SAED investigations also confirm that there are two phases (Fe,Co)2B and Fe (Co,Y) or Fe (Co,Y,B) in the nano-layered structure. The alloy replacing of Y by Nd element has been prepared by suction casting under the magnetic field (~1kOe) and its magnetic measurements show a significant enhancement in Hci (1.1kOe) and Mr/ Ms (0.3).更多还原