Ni-Mn基哈斯勒合金磁致反马氏体相变及磁热效应研究

发布时间：2018-04-27 16:57

本文选题：磁制冷 + 马氏体相变　；参考：《上海电力学院》2017年硕士论文

【摘要】：磁制冷是一种利用磁性材料的磁热效应来实现制冷的新技术,与传统压缩制冷相比,磁制冷技术具备环保、节能、静音的显著优势,有望取代传统压缩制冷技术。目前磁制冷技术已应用于低温制冷,但室温磁制冷技术才刚起步,并且面临很多难题,如诱导相变发生的磁场过大、磁性材料相变过程中磁滞热滞较大、相变可调温区较小等。Ni Mn基哈斯勒合金是一种新型的磁制冷材料,合金在降温过程中,经历了一个从高温奥氏体想到低温马氏体相的相变,并伴随着磁化强度的突变,该相变属于一级相变,研究表明磁化强度的突变可产生一个较大的磁熵变,实现巨磁热相应。在磁制冷技术中,起关键作用的是磁熵,磁性材料的磁熵变化时,伴随着吸热放热的现象以达到制冷效果,但晶格熵和电子熵的存在降低了制冷效率。本文通过利用真空电弧炉制备合金样品Nn50-xCoxMn36Sn14和Ni_(50-x)Co_xMn_(36)In_(14),探讨了Co元素替代Ni位对合金的结构、磁和磁热性能的研究。并比较了不同的替代原子含量对合金的影响,具体如下:第一、二章分别介绍了磁制冷的原理、磁制冷工质熵以及室温磁制冷材料的发展现状、制备方法和材料性能表征的技术手段。第三章研究了Nn50-xCoxMn36Sn14(x=0,0.5,1.5,2,3)合金,发现合金中有温度、磁场诱导的反马氏体相变,并且适量掺杂Co元素可以降低马氏体相变温度,提高居里温度。磁热效应研究表明合金在马氏体相变点附近具有较大的磁熵变,所以合金具有可观的制冷量。另外发现合金的相变温度可伴随Co的掺杂进行调节。通过对样品磁热效应的计算,Ni49.5Co0.5Mn36Sn14的磁熵变达到了18.8 J/(kg K),并且在Ni48.5Co1.5Mn36Sn14中得到了较大的半峰宽,取得了较大的制冷量,最大达到了290.4 J/Kg。第四章主要对元素Co掺杂Ni对Ni_(50-x)Co_xMn_(36)In_(14)(x=2,3,4,5)合金的晶体结构磁相变过程进行分析和研究,结果表明随着Co原子的增加,合金的马氏体相变剧烈程度先增强后消失,同时发现合金的磁化强度显著提高。以热力学理论为基础,计算了合金的等温磁熵变。最大达到了22.7J/(kg K)。第五章研究了Ni_(50-x)Co_xMn_(38)Al_(12)(x=4,6,8)合金,在合金中实现了从铁磁的奥氏体到弱磁的马氏体的马氏体相变,并且得到了磁场诱导的变磁性行为。并且在反马氏体相变得到了较大的磁化强度和磁熵变的变化。通过对样品磁热效应的计算,我们在样品Ni44Co6Mn38Al12中得到了较大的磁熵变,达到了22.3J/(kg K)。第六章对上述内容进行了总结并对目前Ni-Mn基哈斯勒合金的研究前景进行了展望。提出可以在减小热滞和磁滞、提高半峰宽等方面进行改进,提高合金的磁热效应。
[Abstract]:Magnetic refrigeration is a new technology which uses magnetocaloric effect of magnetic material to realize refrigeration. Compared with traditional compression refrigeration, magnetic refrigeration technology has the advantages of environmental protection, energy saving and mute, which is expected to replace the traditional compression refrigeration technology. At present, magnetic refrigeration technology has been applied to low temperature refrigeration, but the room temperature magnetic refrigeration technology has just started, and it faces many difficulties, such as too large magnetic field induced phase transition, large hysteresis and thermal hysteresis in the process of magnetic material transformation. NiMn-based Hassler alloy is a new type of magnetic refrigeration material. During the cooling process, the phase transformation from high temperature austenite to low temperature martensite phase change, accompanied by a sudden change in magnetization. This phase transition belongs to the first order phase transition. It is shown that the sudden change of magnetization intensity can produce a large magnetic entropy change and realize the corresponding giant magnetocaloric change. In the magnetic refrigeration technology, the key role is the magnetic entropy. When the magnetic entropy changes, it is accompanied by endothermic and exothermic phenomena to achieve the refrigeration effect. However, the existence of lattice entropy and electron entropy reduces the refrigeration efficiency. In this paper, the structure, magnetic and magnetocalorimetric properties of the alloy prepared by vacuum arc furnace (VEAF) were investigated by preparing the alloy Nn50-xCoxMn36Sn14 and NiS / NiS / 50 / x / C\ +\ +\ {50\}\%\ The effects of different content of substitution atoms on the alloy are compared as follows: first, chapter two introduces the principle of magnetic refrigeration, the entropy of magnetic refrigerant and the development of magnetic refrigeration materials at room temperature. Preparation methods and technical means for characterization of material properties. In chapter 3, the alloy Nn50-xCoxMn36Sn14Sn14N14xP0. 5 / 1. 5 / 2) is studied. It is found that there is temperature and magnetic field induced anti martensite transformation in Nn50-xCoxMn36-Sn14. The appropriate amount of Co doping can decrease the temperature of martensite transformation and increase the Curie temperature of Nn50-xCoxMn36-Sn14. The study of magnetocaloric effect shows that the alloy has a large magnetic entropy change near the martensitic transformation point, so the alloy has considerable refrigerating capacity. In addition, it is found that the phase transition temperature of the alloy can be adjusted with Co doping. The magnetocaloric effect of Ni49.5Co0.5Mn36Sn14 has been calculated, and the magnetic entropy of Ni49.5 Co0.5Mn36Sn14 has reached 18.8 J/(kg KN, and the larger half peak width has been obtained in Ni48.5Co1.5Mn36Sn14, with a large refrigerating capacity of 290.4 J / Kg. In the fourth chapter, the magnetic transformation process of crystal structure of Ni + Co doped Ni _ 2O _ (50) -x _ (+) _ _ _ At the same time, it was found that the magnetization of the alloy increased significantly. The isothermal magnetic entropy change of the alloy was calculated on the basis of thermodynamics theory. The maximum reached 22.7J/(kg Ke. In the fifth chapter, we study the NiSZ 50-xX CoxMnM) alloy. The magnetic-induced martensite transformation from ferromagnetic austenite to weak magnetic field has been realized in the alloy. The magnetic field induced magnetization behavior has been obtained in the alloy. The results are as follows: (1) in the fifth chapter, we have studied the Nitix 50-x CoxMnM) alloy, and we have obtained the magnetic-induced transformation from ferromagnetic austenite to weak magnetic field. The changes of magnetization and magnetic entropy are also obtained in the anti-martensite transformation. Through the calculation of the magnetocaloric effect of the sample, we have obtained a large magnetic entropy change in the sample Ni44Co6Mn38Al12, which has reached the 22.3J/(kg Ke. In chapter 6, the above contents are summarized and the research prospect of Ni-Mn Kihassler alloy is prospected. It is suggested that the magnetocaloric effect of the alloy can be improved by reducing the thermal hysteresis and magnetic hysteresis and increasing the half peak width.
【学位授予单位】：上海电力学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB64

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