Masahiro Kitada1 and Toshio Doi1
1Central Research Laboratory Hitachi Ltd., Kokubunji
The applied magnetic field vs critical current density, the superconducting transition temperatures and the microstructures of Nb-Zr-Ti-(V,Ta or Mo) alloys have been investigated. V,Mo and Ta added as the fourth elements have BCC structures and are all superconducting. It is presumed that each metal dissolved in the Nb-40Zr-10Ti base alloy is of the substitutional type. The results are as follows: From microstructural observation, the solubilities of V,Ta and Mo are about 5, 5 and 2% in the base alloy, respectively. When the V,Mo or Ta contents are larger than the above values, precipitation occurs and cold working of the alloys becomes more difficult than the base alloy. The critical current densities of Nb-Zr-Ti-(V or Mo) alloys are smaller than that of the base alloy, and the critical current densities of Nb-Zr-Ti-Ta alloys are nearly equal to that of the base alloy. Superconducting transition temperatures of the three alloys containing 5%V, 5%Ta and 5%Mo are 6.7°, 8.4° and 6.3°K, respectively, which are lower than that (9.3°K) of the base alloy.
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