In-Situ Resistance Measurements of RHQT Processed Superconductors

The bcc supersaturated solid solution, obtained by rapid heating and quenching of a multifilamentary Nb/Al composite wire has shown a change from a disordered to an ordered structure before finally transforming to the A15 phase. It is believed that such ordering is responsible for sup- pressing the critical temperature, , the upper critical magnetic field, , and the critical current density, . The ordering of the bcc phase can be suppressed by increasing the heating rate, and therefore this should improve the superconducting properties of the resulting wires. Enhancement of can also be achieved if the phase is mechanically deformed be- fore transformation. The transformation process was studied in as-quenched and mechanically deformed wires by in-situ resistance measurement under heating at two different rates, 200 and 800 . The electrical resistivities of the wires decrease abruptly during the transformation from bcc to A15 phases and the process is much faster for mechanically de- formed wires. Also, the heating rate affects the onset temperature of the A15 transformation. The results also show that the of the transformed wires increases with increasing reduction in area.