Phase Equilibria Determination And Magnetic Properties Of Y-Co-Ti/Zr Alloys

The ThMn₁₂-type rare earth RETM₁₂（RE represents rare earth elements and TM represents transition metal elements）permanent magnet materials have attracted attention due to their excellent intrinsic magnetic properties.However,binary compounds of RETM₁₂ cannot exist stably and require a third element to stabilize the structure.Among them,Ti is a common stabilizing element for TM.Y and Zr replace a portion of the RE to occupy the lattice position 2a,stabilize the ThMn₁₂-type structure,increase the magnetic properties of the compound RETM₁₂,and can also reduce the content of Ti.When magnetic element Co is added to RETM₁₂,it exhibits higher intrinsic magnetic performance.This paper experimentally determined the phase equilibrium of Y-Co-Ti and Y-Co-Zr,and studied the phase structure and magnetic properties of the compound(Y_1-yZr_y)Co_12-xTi_x,obtaining the following results:（1）Using the diffusion couple technique and equilibrium alloy method,in conjunction with scanning electron microscopy（SEM）,electron probe microanalysis（EPMA）,and X-ray diffraction（XRD）techniques,the isothermal sections of the Y-Co-Ti ternary system at 600°C and 800°C have been determined.A total of seventeen binary compounds were observed in the system,including Y₂Co₁₇,YCo₅,Y₂Co₇,YCo₃,YCo₂,Y₂Co₃,Y₆Co₇,YCo,Y₄Co₃,Y₈Co₅,Y₃Co,Co₃Ti,Co₂Ti（h）,Co₂Ti（c）,Co Ti and Co Ti₂.Additionally,the ternary intermetallic compound YCo_12-xTi_x with a ThMn₁₂-type structure was found to exist stably,with a composition range of 8.3-18.2 at.%Ti at 600°C and 8.9-19.1 at.%Ti at 800°C.（2）The isothermal sections of the Y-Co-Zr ternary system at 800°C and 600°C were determined using the diffusion couple technique and equilibrium alloy method,combined with scanning electron microscopy（SEM）,electron probe microanalysis（EPMA）,and X-ray diffraction（XRD）techniques.Sixteen binary compounds were observed in the system,including Y₂Co₁₇,YCo₅,Y₂Co₇,YCo₃,YCo₂,YCo,Y₄Co₃,Y₃Co₂,Y₈Co₅,Y₃Co,Co₁₁Zr₂,Co₂₃Zr₆,Co₂Zr,Co Zr,Co Zr₂ and Co Zr₃.No ternary intermetallic compounds were found.Due to their identical crystal structures,YCo₂and Co₂Zr formed a continuous solid solution phase（Y,Zr）Co₂ with a Cu₂Mg-type structure.（3）The phase composition,structure,and magnetic properties of YCo_12-xTi_x（x=0.9～2.4）and Y_1-yZr_yCo_10.2Ti_1.8（y=0.05～0.25）in the as-cast and quenched thin strip states were studied using scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and vibrating sample magnetometer（VSM）techniques.The results showed that the YCo_12-xTi_x alloy was composed of a 1:12 phase when the Ti content was 1.8.Using VSM to detect YCo_12-xTi_x quenched thin strips,the magnetic properties did not improve with heat treatment.The magnetic properties of Y_1-xZr_yCo_10.2Ti_1.8（y=0.05～0.25）alloy doped with Zr elements were significantly improved,and a maximum coercivity of 0.71 k Oe was obtained after heat treatment at 400℃for 15minutes.