【作者】 王伟；

【导师】 刘国栋；

【作者基本信息】 河北工业大学 ， 工程硕士（专业学位）， 2019， 硕士

【摘要】 在磁性形状记忆合金中,温度、应力和磁场都可能诱导马氏体相变或者马氏体变体重排,从而带来巨大的应变效应、吸放热效应、磁感生应变以及输运性质等物性的剧烈变化。此类材料在磁机、磁电、磁制冷等多个领域具有巨大的应用前景。耦合应力和磁场、应力和温度,共同作用于磁性形状记忆合金,能够有效的改善和提高材料的某些应用性能:比如能够扩大磁场诱导马氏体相变的温区等。巨磁致伸缩材料在磁场下能够提供巨大的应力和应变。将巨磁致伸缩材料与磁性形状记忆合金复合,能够在不借助外加装置的情况下,给磁性形状记忆合金施加应力,将磁场和应力共同作用于磁性形状记忆合金。本论文工作首先围绕Tb_0.27Dy_0.73Fe_1.9/Fe复合材料和Tb_1-xNd_xFe₃（x=0-1）系列合金展开。研究巨磁致伸缩材料在形成复合材料后,烧结工艺对磁致伸缩性能的影响。进而将磁性形状记忆合金与巨磁致伸缩材料复合,研究在巨磁致伸缩材料提供应力作用下,应力和磁场耦合作用对磁性形状记忆合金的物性影响。通过实验取得了一些对材料实际应用具有指导意义的结论,主要发现如下:对Tb_0.27Dy_0.73Fe_1.9/Fe复合材料磁致伸缩性能的研究发现,等离子烧结过程中的压应力会对材料的磁致伸缩性能产生影响,垂直于压力方向的磁致伸缩性能优于平行于压应力方向的磁致伸缩性能。Tb_0.27Dy_0.73Fe_1.9/Fe复合材料的饱和磁致伸缩系数随着Fe含量的增加而降低,然而当Tb_0.27Dy_0.73Fe_1.9和Fe的体积比为4:1时,复合材料在低场的磁致伸缩并未降低,可见Fe的加入的确起到了辅助外加磁场增强磁化的作用。利用电弧熔炼合成了Tb_1-xNd_xFe₃（x=0-1）系列合金,研究发现当Nd含量低于0.6时,合金的主相均为Pu Ni₃型立方结构。磁性测量表明,合金的饱和磁化强度随着Nd含量的增加呈现出先降低而后增加的变化趋势。磁致伸缩测量的结果发现,Nd掺杂合金的饱和磁致伸缩均低于Tb Fe₃合金的饱和磁致伸缩,然而在磁场低于2000 Oe时,Tb_0.6Nd_0.4Fe₃合金的磁致伸缩性能却优于Tb Fe₃合金的磁致伸缩性能,该合金有望成为低场应用磁致伸缩的候选材料。对于Ni₅₂Mn_24.5Ga_23.5/Tb_0.27Dy_0.73Fe_1.9与Ni₅₂Mn_24.5Ga_23.5/Tb Fe_1.9等离子烧结体马氏体相变特性的研究发现,Tb_0.27Dy_0.73Fe_1.9与Tb Fe_1.9掺入后扩大了马氏体相变温区,并且对马氏体相的结构产生了影响。然而,等离子烧结体的马氏体相变并未受到外加磁场的影响,与同成分Ni₅₂Mn_24.5Ga_23.5/Tb_0.27Dy_0.73Fe_1.9粘结体对比发现,该类等离子烧结体中马氏体相变行为是受到Tb_0.27Dy_0.73Fe_1.9合金居里温度处自发形变的影响。更多还原

【Abstract】 In the magnetic shape memory alloys,temperature,stress and magnetic field may induce martensitic transformation or martensitic variant rearrangement,resulting in drastic changes in physical properties such as strain effect,endothermic and exothermic effect,magnetic induced strain and transport properties.This kind of material has great application prospects in many fields such as magnet,magnetoelectrics,magnetic refrigeration and so on.The coupling stress,magnetic field,stress and temperature act together on magnetic shape memory alloy,which can effectively improve some application properties of materials,for example,the temperature range of martensitic transformation induced by magnetic field can be enlarged.Giant magnetostrictive materials can provide tremendous stress and strain under magnetic field.The composite of giant magnetostrictive material and magnetic shape memory alloy can exert stress on magnetic shape memory alloy and make the magnetic field and stress act together on magnetic shape memory alloy without the aid of external device.Firstly,this thesis focuses on Tb_0.27Dy_0.73Fe_1.9/Fe composites and Tb_1-xNd_xFe₃（x=0-1）series alloys.The effect of sintering process on magnetostrictive properties of giant magnetostrictive materials after forming composite materials was studied.Then the magnetic shape memory alloy and giant magnetostrictive material were compounded to study the effect of stress and magnetic field coupling on the physical properties of magnetic shape memory alloy under the stress of the giant magnetostrictive material.Some conclusions which have guiding significance for the practical application of materials have been obtained through the experiment.The main findings are as follows:The magnetostrictive properties of Tb_0.27Dy_0.73Fe_1.9/Fe composites were studied.It was found that the compressive stress affected the magnetostrictive properties of the composites during plasma sintering.The magnetostrictive properties perpendicular to the pressure direction are better than those parallel to the compressive stress direction.With the increase of Fe content,the saturation magnetostriction coefficient of Tb_0.27Dy_0.73Fe_1.9/Fe composite decreases.However,when the volume ratio of Tb_0.27Dy_0.73Fe_1.9 to Fe is 4:1,the magnetostriction of the composites does not decrease in the low field.It can be seen that the addition of Fe does play an auxiliary role in enhancing magnetization by external magnetic field.Tb_1-xNd_xFe₃（x=0-1）series alloys were composed by arc melting.It was found that when the Nd content was less than 0.6,the main phase of the alloys was PuNi₃ cubic structure.The magnetic measurements show that the saturation magnetization of the alloy decreases first and then increases with the increase of Nd content.The results of magnetostriction measurements show that the saturation magnetostriction of Nd-doped alloys is lower than that of TbFe₃ alloys.However,when the magnetic field is lower than2000 Oe,the magnetostrictive properties of Tb_0.6Nd_0.4Fe₃ alloy are better than that of TbFe₃ alloy,which is expected to be a candidate material for magnetostrictive applications in low field.The martensitic transformation characteristics of Ni₅₂Mn_24.5Ga_23.5/Tb Fe_1.9 and Ni₅₂Mn_24.5Ga_23.5/Tb_0.27Dy_0.73Fe_1.9 plasma sintered bodies were studied.It was found that the incorporation of Tb_0.27Dy_0.73Fe_1.9 and Tb Fe_1.9 enlarged the martensitic transformation temperature range and affected the structure of martensitic phase.However,the martensitic transformation of plasma sintered alloys is not affected by the external magnetic field.Compared with the Ni₅₂Mn_24.5Ga_23.5/Tb_0.27Dy_0.73Fe_1.9 binder of the same composition,it is found that the martensitic transformation behavior of plasma sintered alloys is affected by the spontaneous deformation at Curie temperature of Tb_0.27Dy_0.73Fe_1.9 alloy.更多还原