The Reaction of Solid Cobalt with Molten Copper. II : On the Migration of Molten Copper into Solid Cobalt and the Structure of Copper-Cobalt Interface

A basic investigation on the cobalt brazing has been made of the migration of molten copper into solid cobalt and of the structure of copper-cobalt interface in the temperature range of 1100°-1300℃ for the reaction time of 0～30min. The reaction between molten copper and solid cobalt proceeds with the temperature and the reaction time. The principal mechanism of the migration of molten copper into solid cobalt is shown to be by volume diffusion. Initial rate of penetration has the values of 0.4 to 1.1×10^ mm/min. The penetration depth increases proportionally with the square root of the reaction time and the obtained value of the penetration-rate constant is 2.5～7.3×10^ mm/min^. The activation energy for penetration was estimated to be about 23.5kcal/mole. In the liquid-solid interface region, some solid-metal dendrites within the liquid and a relatively thick dendrite layer on the liquid side at the interface were crystallized during solidification and on the opposite side of this interface, a thick solid-solution layer penetrated by molten metal was recognized