Abstract: The microstructure, texture and magnetic properties of99.999% 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 (∑3 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.

Key words: high purity Co target, microstructure, magnetic permeability, ferromagnetism