Preparation of Nb3Al superconductor by powder metallurgy and effect of mechanical alloying on the phase formation

摘要

Abstract Adoption of powder-in-tube method to fabricate superconducting wire can realize a large application of Nb~(3)Al prepared by powder metallurgy. Powder metallurgy was used to synthesize Nb~(3)Al under various heat-treatment conditions, annealing temperature was varied from 700 to 1,000?°C and heating time was varied from 10 to 50?h. X-ray diffraction patterns reveal that a reaction between Nb and Al took place and formed NbAl~(3) phase. Under current heat-treatment conditions (annealing temperature was varied from 700 to 1,000?°C and heating time was varied from 10 to 50?h), NbAl~(3) was so stable that it did not further react with the unreacted Nb and was not sensitive to the heat-treatment condition. By mechanical alloying, adoption of high-energy ball milling significantly decreases particle size and enhances surface free energy, which promotes the formation of Nb~(3)Al phase. X-ray diffraction patterns indicate that relatively pure Nb~(3)Al phase was obtained under the same heat-treatment condition. Energy-dispersive X-ray analysis measurement demonstrates that the obtained samples were close to the right stoichiometry of A15 structure Nb~(3)Al.