Comparison of Ta3wt%W and Pure Ta as a Wire Reinforcement Element in a Multifilament Composite

In very high field magnetic applications, the windings can see very high Lorentz forces. One way to support a reacted Nb3 Sn wire under high loads is to reinforce the conductor with a high strength, high modulus element in the composite. This has been done previously with pure Ta as well as Cu-Nb multifilament elements. This work compares the results of using Ta3wt%W with pure Ta or pure Cu to reinforce a Cu-Nb multifilament conductor meant to mimic the processing of a Nb3 Sn internal tin type composite. Ta3wt% W is found to provide higher strength than pure Ta to the composite and be compatible with drawing to small diameters. A Ta3wt% W core element was successfully drawn with the Cu-Nb assembly to a diameter of 120 μm. The addition of tungsten to the tantalum also improves the microstructure of the tantalum and results in less interface distortion during processing. The mechanical properties and hardness of the individual elements were monitored during the wire processing to look at work hardening rates. A 2.7% area core made of Ta3wt%W provided more than 10% increase in the mechanical strength of the wire over a copper core and provided twice the strength increase of the same size pure tantalum core.