Grain size in A-15 reaction layers

Grain sizes of Nb3Sn, V3Ga, and V3Si made by the bronze technique are measured by transmission electron microscopy of multifilamentary composites reacted at various temperatures. Grain sizes of V3Ga are found to be larger than those of Nb3Sn and V3Si formed at the same temperature, but much smaller than those reported by earlier workers. Copper contents of the A-15 layers are found to be low. Critical current densities at 4.2 K and fields up to 6 T are similar for V3Ga, Nb3Sn, and V3Si of the same grain size.