PRODUCTION OF CO-CU-BE ALLOY FIBER BY IN- ROTATING-WATER-SPINNING PROCESS AND ITS SOLIDIFICATION STRUCTURE

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 mech anical 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 add ed. To produce a long wire, it was important to quickly eject the melt through a nozzle with high reduction before heavy reaction of the mol ten alloy with the quartz nozzle. In the case of 5 similar to 50 at%Cu alloys, finer dendritic structures of Co-rich phase caused by rapid c ooling were observed and the secondary dendrite arm spacing varied inv ersely as about the cubic root of cooling rate. The secondary dendrite arm spacing decreased with increasing Cu concentration and such a ten dency agreed roughly with the calculated result. In the case of 60 sim ilar to 80 at%Cu alloys, granular structures separated into the Co-ric h and Cu-rich phases were observed. Because these structures are forme d by the result of undercooling below the liquid immiscibility tempera ture 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. Th e elongation of rapidly solidified wire was about 20% for the 5 at%Cu wire and decreased with increasing Cu concentration. In the case of th e separated two-phase structure, the elongation was lower than about 5 %, but the ductility was high enough to be bent through 180 degrees wi thout fracture. The tensile strength was in the range from 300 to 600 MPa.