Properties of microfilamentary superconducting composites produced by a modified external diffusion method

Nb/sub 3/Sn-based bronze matrix superconducting composites have been produced with micro-sized and submicron-sized superconducting fibers by the external diffusion process, with precautions taken as recently recommended to suppress Kirkendall porosity. Such composites were found to carry overall critical current densities at 4.2/degree/K in excess of 2*10/sup 4/ a/cm/sup 2/ at 15.4 T and over 10/sup 5/ a/cm/sup 2/ at 12 T; strains ca. 2% and stresses in the 500-1000MPa range were sustained without degradation. It is seen that the finer fibers sustain higher intrinsic strains before degradation of J/sub c/. A method is demonstrated for the control of internal residual stresses by thermomechanical processing. The latter permits appropriate trade offs of fatigue life and zero-strain J/sub c/. 12 refs