热处理制度对高纯钴微观组织及磁性能的影响

Influence of heat treatment on microstructure and magnetic properties of high purity cobalt

对99.999%高纯钴进行350、450和550℃的热处理,利用光学显微镜、电子背散射衍射技术及振动样品磁强计分析了热处理后高纯钴的微观组织、织构及磁性能。结果表明,热处理温度对高纯钴的相含量、晶界含量及晶粒织构有明显的影响,350℃热处理后的组织全部为密排六方相(HCP相),具有较强的织构;在相变温度427℃以上的450和550℃热处理后的组织为HCP相和FCC相两相共存,小角度晶界占比急剧降低,大角度晶界占比大幅提升,并产生了两种特殊晶界:相变孪晶界70.5°/<1120>和退火孪晶界(∑3晶界)60°/<111>。高纯钴经350℃热处理后的组织极密度最大,[0001]织构含量最大,且相对磁导率最低,为6.1。当高纯钴在相变温度以上热处理时,磁导率大幅升高。

The microstructure,texture and magnetic properties of 99.999%high purity cobalt after heat treated respectively at 350,450 and 550℃were analyzed by means of optical microscope,electron backscatter diffraction and vibrating sample magnetometer.The results show that the phase,grain boundary and grain texture of the high purity cobalt are significantly affected by the heat treatment temperature.When the heat treatment temperature is 350℃,the microstructure of the high purity cobalt is HCP phase with strong texture.When the heat treatment temperature are 450℃and 550℃which are above the phase⁃transition temperature of 427℃,the microstructure is the coexistence of HCP phase and FCC phase,the fraction of small angle grain boundaries decreases sharply,the large angle grain boundaries increase significantly,and producing two special grain boundaries:phase transition twin boundary of 70.5°/<1120>,and annealing twin boundary(Σ3 grain boundary)of 60°/<111>.When the heat treatment temperature is 350℃,the pole density and[0001]texture content of the high purity cobalt are the highest and the relative permeability is the lowest as 6.1,while when the heat treatment temperature is above the phase⁃transition temperature,the permeability of the high purity cobalt increases significantly.