Process development and microstructures of Nb3Al precursor strand for reel-to-reel production

Niobium-aluminun precursor strands were fabricated using a modified form of the rod-in-tube method (MRT) and also the conventional jelly- roll (JR) me thod. Monoelements with Nb/Al volume ratios of 2.3, 2.7, 3, and 5 were draw n down and restacked into groups of 7x37 and 37x37 (MRT), also 7, 19, and 3 6 (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, thicknes s of the Al component of the Nb/Al composite was reduced to sizes in the ra nge of 2.5 to 0.1 mu m Although most of the material produced to date has b een fully cold drawn, Harm hyhrostatic extrusion has been explored for Lee in the next phase of strand production. The MRT and JR strands, in short-sa mple form have been subjected to pulsed resistive heating to temperatures o f typically 1800 to 2100 degrees C followed by either radiative cooling or liquid-Ga quenching, Studies of the relationship between Al-element thickne ss and final properties have been made.