Investigations of the wettability and the interaction between solids and liquids in Cu-Sn binary system were carried out in the atmosphere of dry hydrogen gas flow by coupling solid pure copper, ε(Cu₃Sn) and η(Cu₆Sn₅) alloy plates with liquid pure tin and Sn-Cu alloys respectively. The results obtained were as follows:
(1) Wetting angle between solid pure copper and liquid pure tin showed a tendency to decrease with the passage of time at the temperature between 523 and 623 K. On the contrary, wetting angle between solid pure copper and liquid pure tin more than 623 K or that between solid alloy plates (ε or η) and liquid drops (pure tin or Sn-Cu alloy) at the temperature between 573 and 773 K did not have the time dependency.
(2) Wetting angle between solid pure copper and liquid pure tin showed a remarkable discontinuity in the vicinity of peritectic temperature (η=ε+melt); from our experiment it is reasonable to consider that the above peritectic temperature is higher than that of already known 668 K.
(3) At each temperature in the present experiment, it has been clarified that the smaller the defference of concentration between solid and liquid in Cu-Sn binary system, the smaller the wetting angle; in other words, the nearer the concentration of solid plates to that of liquid drops, the more wettable.