Comparison of Al5-Nb/sub 3/Al superconductors produced by laser alloying and infiltration

Nb/sub 3/(Al, Si, Bi) and Nb/sub 3/Al superconductors were successfully prepared by a laser alloying and an infiltration process. Continuous CO/sub 2/ laser irradiation of Nb-sheathed Nb-25-at.% Al composite tapes prepared by a conventional powder metallurgical method was carried out. For a laser power of less than 3.5 kW and specimen velocities up to 30 m/min, almost stoichiometric Nb/sub 3/Al with critical temperatures of 16.6 K and critical current densities of 10/sup 4/ A/cm/sup 2/ at 15 T was obtained. For infiltration, sintered Nb powder was immersed in a liquid (Al/sub 88.7/Si/sub 11.3/)/sub 99/Bi/sub 1/ alloy. Subsequently the infiltrated rod was deformed and reacted at temperatures up to 2000 degrees C. The microstructure and the superconducting properties have been studied as a function of the degree of deformation and the reaction temperature. Critical temperatures between 14 and 18 K, upper critical fields B/sub c2/ of 21 T and critical current densities of 10/sup 4/ A/cm/sup 2/ at 16 T were obtained.<
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