Process development and microstructures of Nb/sub 3/Al precursor strand for reel-to-reel production

Niobium-aluminum precursor strands were fabricated using a modified form of the rod-in-tube method (MRT) and also the conventional jelly-roll (JR) method. Monoelements with Nb/Al volume ratios of 2.3, 2.7, 3, and 5 were drawn down and restacked into groups of 7/spl times/37 and 37/spl times/37 (MRT), also 7, 19, and 36 (JR) elements. Suitably clad, these were reduced to final strand sizes of 1.6, 1.2, and 0.8 mm (MRT) also 0.8 and 0.4 mm (JR). In this way, the thickness of the Al component of the Nb/Al composite was reduced to sizes in the range of 2.5 to 0.1 /spl mu/m. Although most of the material produced to date has been fully cold drawn, warm hydrostatic extrusion has been explored for use in the next phase of strand production. The MRT and JR strands, in short-sample form, have been subjected to pulsed resistive heating to temperatures of typically 1800 to 2100/spl deg/C followed by either radiative cooling or liquid-Ga quenching. Studies of the relationship between Al-element thickness and final properties have been made.