On the suppression of Kirkendall porosity in multifilamentary superconducting composites

The effect of hydrostatic pressure during reaction heat treatment on Kirkendall porosity in Nb3Sn multifilamentary composites is examined. Above a critical pressure which is a function of wire size, void formation is suppressed, and at higher pressures voids already present may be healed. The critical pressure is relatively low, 300-500 psi for 0.010" wire, for external diffusion.