Effect of the heat treatment on the structure and the properties of the electroless CoFeB alloy

The CoFeB alloy was electrolessly deposited from the solution using potassium borohydride (KBH4) as a reducing agent and ethylenediamine as the stabilizer. The crystallization behavior of the alloy coating was studied by using the differential scanning calorimetry and X-ray diffraction. The structure of the as-plated deposit is amorphous. The deposit was converted into Co3B and CoFe phases at 464.9 °C. The effect of the heat treatment on the surface morphology, the magnetic properties and the microhardness of the CoFeB deposit were investigated. As a result, the microhardness and the magnetic performances of the deposit rise with the increase of the heat treatment temperature up to 500 °C, then they decrease. The deposit treated at 500 °C consists of nano-grains (the size of the grains is about 20 nm), and has optimal magnetic properties.