Research On Construction Of Temperature-composition Phase Diagram Of Cubic Laves Phase Alloy Based On Light Rare Earth(Pr Nd)

Magnetostrictive materials are important magnetic functional materials for manufacturing transducers and sensors.They play an important role in key components and core systems in national economy and national defense fields.However,terfenol-D material with precious heavy rare earth materials(such as Tb and Dy)as the main raw material has complex preparation process,high commodity price and high intrinsic brittleness.However,the materials with relatively cheap light rare earth materials(such as Pr and Nd)as the main raw materials have large magnetostriction at low temperature,but also have large magnetocrystalline anisotropy,so it is difficult to obtain large magnetostriction at low field.These factors limit the wide application of rare earth materials,and there are still many blind spots about the inner physical mechanism of rare earth smart alloys.Recently,as a relatively new research direction,Morphotropic Phase Boundary(MPB)has been successfully introduced into cubic Laves Phase rare earth alloy,which has injected new vitality into the research of rare earth magnetostrictive materials.The quasisomorphic phase boundary refers to an area where tetragonal phase and tripartite phase coexist.The energy of the two phases is close,but the crystal structure is different.Near the quasisomorphic phase boundary,the free energy of the two phase states is similar.To design MPB materials,it is necessary to select two materials with different crystal structures(or easily magnetized directions(EMD))as the end materials to construct MPB system.For most of the Laves phase rare earth alloys,the crystal structure changes with the temperature change.Therefore,it is an important research content to study the penisomorphic phase boundary and the temperature-composition phase diagram of the end-materials of Laves phase rare earth alloy.Laves phase rare earth compounds with different crystal structures(or EMD along[111]and[100])are selected to construct magnetic MPB systems under the guidance of temperaturely-component phase diagrams,which is a new method to obtain intelligent materials with the highest external field response and sensitivity.At the same time,it is of great significance for us to have a deep understanding of the magneto-elastic mechanism of the ferromagnetic material quasisomorphic phase boundary,and to guide and design giant magnetostrictive materials.In this paper,we mainly studied the construction of temperature-composition phase diagram of Pr(Ga_xFe_1-x)_1.9alloy?Pr(Fe_1-xCo_x)_1.9alloy and Pr_xNd_1–xFe_1.9alloy from three aspects as follows:1.Research on construction of temperature-composition phase diagram of Pr(Ga_xFe_1-x)_1.9alloyMgCu₂cubic Pr(Ga_xFe_1-x)_1.9alloy with Laves phase structure was prepared by high pressure annealing.The Curie temperature(T_C)and spin reorientation temperature(T_SR)of the alloy can be decreased by Ga replacing Fe.In Pr(Ga_xFe_1-x)_1.9alloy at room temperature(RT),the content of Ga increases,and the magnetostriction continues to decrease.However,the substitution of Ga for Fe at 5K reduces the magnetostriction of the alloy at10?H?90k Oe high magnetic field and increases at 0?H?10k Oe low magnetic field,suggesting that the substitution of Ga for Fe at 0.02?x?0.05 at low magnetic field can enhance the magnetostriction of the alloy.When the temperature drops from 300 K to 15 K,the easy magnetization direction of the alloy changes from[111]to[100]at the spin reorientation temperature T_SR.The analysis of Mossbauer spectrum shows that the easy magnetization direction will change from[111]direction to[100]direction at low temperature.The temperature-component phase diagram of Pr(Ga_xFe_1-x)_1.9alloy was constructed by Curie temperature(T_C)and spin reorientation temperature(T_SR).2.Research on construction of temperature-component phase diagram of Pr(Fe_1-xCo_x)_1.9alloyA single MgCu₂cubic Laves phase structure Pr(Fe_1-xCo_x)_1.9series alloy was prepared by high pressure annealing.The effects of Co doping on the crystal structure,magnetic properties and M?ssbauer spectra of Laves phase Pr(Fe_1-xCo_x)_1.9alloy were investigated.The results of precision scanning XRD show that the characteristic peaks{222}and{440}of Pr(Fe_0.8Co_0.2)_1.9alloy are split between 300K and 130K,indicating that the easy magnetization direction of the alloy is[111].In the range of 100K?20K,the characteristic peaks{222}do not split and{440}do split,and the easy magnetization direction is[100],indicating that the easy magnetization of the alloy changes at low temperature.However,the direction of easy magnetization of M?ssbauerr spectrum at room temperature is[111],indicating that Co doping at room temperature has no effect on the direction of easy magnetization of the alloy.The temperature-component phase diagram of Pr(Fe_1-xCo_x)_1.9alloy was constructed by Curie temperature and spin reorientation temperature.3.Research on construction of temperature-component phase diagram of Pr_xNd_1-xFe_1.9alloyThe crystal structure of Pr_xNd_1-xFe_1.9alloy with cubic Laves phase has been studied by Mossbauer spectra.The temperature range is 15K to 300K by step fine scanning X-ray diffraction(XRD)analysis.The results show that the O+R phase(PMB)appears when the Pr content is 0.2 at 100K,and the O+R phase O+T phase(PMB)appeared when Pr content was 0.4 at 15K?100K.M?ssbauer spectrum analysis shows that the direction of easy magnetization will change from[110]to[111]direction at low temperature when x?0.6.The temperature-component phase diagram of Pr_1-xNd_xFe_1.9alloy was constructed by Curie temperature and spin reorientation temperature.