Comparison of Al5-Nb₃Al superconductors produced by laser alloying and infiltration

Nb₃(Al, Si, Bi) and Nb₃Al superconductors were successfully prepared by a laser alloying and an infiltration process. Continuous CO₂ 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 Nb₃Al with critical temperatures of 16.6 K and critical current densities of 10⁴ A/cm² at 15 T was obtained. For infiltration, sintered Nb powder was immersed in a liquid (Al_88.7Si_11.3)₉₉Bi₁ alloy. Subsequently the infiltrated rod was deformed and reacted at temperatures up to 2000°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_c2 of 21 T and critical current densities of 10⁴ A/cm² at 16 T were obtained