Research on the Monolithic Process of Making A-15 Superconducting Materials

摘要

It is possible to produce high T/sub c/ wires or tapes from the V-Ga system by a monolithic process in which an ingot is cast as a supersaturated solution of V and Ga, homogenized at elevated temperature, quenched to preserve the supersaturation, formed into a wire or tape, and finally heat treated at a relatively low temperature to precipitate the superconducting phase. To achieve exceptionally high critical temperatures, the precipitation reaction must be carried out at temperatures below approximately 750 exp 0 C. The measured critical temperature then becomes a function of the aging time, and reaches a maximum value as high as 14.8 exp 0 K in alloys containing 17 to 19 at. % Ga. The reason for the exceptionally high critical temperature when the precipitation is carried out at lower aging temperatures is not established, but may be plausibly interpreted as due to a thermodynamic tendency for small precipitates formed from highly supersaturated solid solutions to be rich in solute content. (ERA citation 05:013890)