On the Dissolution of Copper in Liquid Tin

Abstract

A static study has been made on the process of dissolution of copper into liquid tin under static and isothermal conditions. The results obtained from the experiments made at 14 different temperatures ranging from 340° to 750°C are summarized as follows:
(1) Because of the large solubility limit of the system, dissolution velocities are very large: About two minutes after dipping, solute concentrations of the liquid at definite temperatures attain 90% of solubility limits for these temperatures.
(2) In such systems having large solubility limits as in the case of the Cu-Sn system, rate constants of dissolution can be calculated by Eqs. (14) and (12).
(3) At temperatures between 340° and 427°C, the rate constant of dissolution increases with increasing temperature, but it decreases almost monotonously with increasing temperature from 450° to 540°C except that it shows a small maximum at about 518°C. This particular trend may be explained by the facts that the phases contacted with the liquid metal are η for the lower and ε for the higher temperature range. Further, the fact that the solution rate constants measured are 5∼20×10⁻³ mm/sec and are larger than in other systems measured under static conditions, is attributed to large natural convections produced by large density differences in the present system.
(4) At 340°∼427°C, 518° and 586°C, the rate of dissolution is determined by diffusion of Cu atoms in the effective boundary layer of liquid metal near the solid surface. In the range 450°∼540°C, however, the rate is determined by the surface reactions of Cu atoms jumped into the liquid.
(5) Owing to the natural convections caused by the density differences, the dissolution velocity of the upper part of the specimen is larger than that of the lower part.