Abstract
This paper presents the effects of addition of Be on the spinnability of Co-Cu alloys in a concentration range from 5 to 97 at%Cu in the In-Rotating-Water-Spinning process, the solidification structure and mechanical properties of obtained wires. Wires longer than 1.5 m with high roundness in the cross-section could be produced when 5 at%Be was added. To produce a long wire, it was important to quickly eject the melt through a nozzle with high reduction before heavy reaction of the molten alloy with the quartz nozzle. In the case of 5∼50 at%Cu alloys, finer dendritic structures of Co-rich phase caused by rapid cooling were observed and the secondary dendrite arm spacing varied inversely as about the cubic root of cooling rate. The secondary dendrite arm spacing decreased with increasing Cu concentration and such a tendency agreed roughly with the calculated result. In the case of 60∼80 at%Cu alloys, granular structures separated into the Co-rich and Cu-rich phases were observed. Because these structures are formed by the result of undercooling below the liquid immiscibility temperature through rapid cooling, it is estimated that the undercoolings of about 80 K or more occur in this process. In the case of 90 and 97 at%Cu alloys, dendritic structures of the Cu-rich phase were observed. The elongation of rapidly solidified wire was about 20% for the 5 at%Cu wire and decreased with increasing Cu concentration. In the case of the separated two-phase structure, the elongation was lower than about 5%, but the ductility was high enough to be bent through 180 degrees without fracture. The tensile strength was in the range from 300 to 600 MPa.
