Crystallization Mechanism of Co77B23 Amorphous Alloy

Crystallization behavior of Co77B23 alloy at increasing temperature has been studied using resistivity measurements and auger-electron spectroscopy. The amorphous nature of the specimen ribbon was ascertained by X-ray diffraction analysis. The resistivity measurements showed a gradual increase of resistivity with temperature, which at about 600 K showed an abrupt fall in its value due to the onset of crystallization. As the heating continued, more peaks at different temperatures were detected in the resistivity-temperature distribution curve. These were identified as belonging to other phase changes in the crystallized alloy. Auger-electron analysis has been made to investigate chemical composition changes during heating. The results show a decrease in boron content on surface layers, which points to an inward diffusion of boron atoms. An excess of cobalt atoms is left on the surface, making the amorphous layers on the surface unstable, which leads to crystallization.