Study On Phase Diagram Of M-Nb-Ru（M=Co,Cr） Ternary System And Crystal Structure,Absorbing Properties Of Cr₂NbRu₂

With the continuous development of science and technology,high performance alloy materials have become indispensable structural materials in the industry.However,the application of many materials has basically approached the limit of technology at present.Because of its relatively high melting point and room temperature ductility,Nb base alloy has great research prospects as high-temperature structural refractory materials.Therefore,alloying to improve Nb base alloy has become a research focus,while Co and Cr alloys have excellent corrosion resistance and oxidation resistance,and Ru can improve the stability of microstructure at high temperature,thus improving the creep strength,so as to improve the properties of Nb base through alloying.The ternary system M-Nb-Ru（M=Co,Cr）,which has not been reported in depth at present,meets the requirements.Therefore,this paper studies the isothermal section of the ternary system Co-Nb-Ru at 1100℃,and finds a method to judge and accurately measure the miscibility gap in the process of studying the phase diagram.The miscibility gap of Nb and Cr in Ru is determined by this method.In addition,the crystal structure of Cr₂NbRu₂ was analyzed by Rietveld method,and it was found that the compound has good absorbing property.The main conclusions are as follows:（1）The phase diagram of 1100℃isothermal section of Co-Nb-Ru ternary system was determined by ternary diffusion and equilibrium alloy method,the isothermal section is composed of 11 single-phase regions,22 two-phase regions,and 12 three-phase regions.Three new terrains have been discovered,τ1（Co₄Nb₃Ru₃）,τ2(Co₁₆Nb₉Ru₁₅)andτ3(Nb(Co_xRu_1-x)3,0.08<x<0.36).In addition,the solid solution range of the phase was measured accurately.（2）The invention provides a method for judging and accurately measuring miscibility gap,the miscibility gap of Cr-Nb-Ru ternary system was determined.The diffusion couple method can be used to intuitively observe the corresponding diffusion layer in the diffusion couple.Combining with the composition range of each diffusion layer,it can accurately determine whether there is a miscibility gap by comparing with the existing phase diagram.The invention uses an electron probe to make a series of evenly spaced component points near the boundary of the diffusion layer perpendicular to both sides of the boundary to obtain the component distance curve.By extrapolating the component distance curve to the boundary of the diffusion layer,the boundary range of the miscibility gap at a specific temperature can be accurately obtained.The method of the invention can simultaneously study the miscibility gap problem of three binary phase diagrams by preparing a ternary diffusion node;By measuring a series of component distance curves at the boundary of the diffusion region,the miscibility gap region of the ternary isothermal section can be accurately obtained.（3）A new phase Cr₂NbRu₂ was prepared by arc melting and its crystal structure was obtained by Rietveld method after refining the X-ray powder diffraction data.The crystal structure of the ternary compound is modeled by Ag₅Zn8 cubic structure（space group I-43m No.217）.The cell parameters:a=b=c=0.93377（1）nm,α=β=γ=90。,Z=2,Dcalc=9.5837g/cm3.（4）The absorption performance of the new phase Cr₂NbRu₂ is studied.It is found that the optimum reflection loss（RL）of Cr₂NbRu₂is-31.20d B and the effective bandwidth is1.76GHz when the matching thickness is 1.8mm and Cr₂NbRu₂ is 14.8GHz.Fe,Co and Ni were used to replace the rare metal Ru element in Cr₂NbRu₂,respectively equipped with Cr₂NbRu_（2-x）Fe_x,Cr₂NbRu_（2-x）Co_x and Cr₂NbRu_（2-x）Ni_x.It is found that the optimal reflection loss is-25.85d B（absorptance>99%）and effective bandwidth is（RL<-10 d B）2.64GHz when the Fe doping amount is 0.4 and the matching thickness is 1.8mm.When the Co content is 0.4 and the matching thickness is 1.8mm,the reflection loss at 9.44GHz is-31.06d B（absorptior greater than 99%）,and the effective bandwidth is（RL<-10 d B）1.64GHz.When the Ni content is 0.3,the matching thickness is 1.6mm,and the frequency is 10 GHz,the optimal reflection loss is-46.10d B（absorptivity is greater than 99%）,and the effective bandwidth（RL<-10 d B）is 1.28 GHz.It can be seen that appropriate addition of Fe,Co and Ni can make the reflection loss move to low frequency successfully,and the addition of Fe improves the effective bandwidth,and the addition of Ni increases the reflection loss.