Effect of heat treatment on critical current density in multifilamentary Nb46.5Ti/Cu composites at high magnetic fields

A lower temperature pre-heat treatment process was used to study the effects of heat treatment on microstructure and critical current densities in Nb46.5Ti multifilamentary composites. The results show that pre-heat treatment at lower temperature (such as 375°C) is beneficial to refining α-Ti particles and sub-bands, furthermore dispersing α-Ti particles throughout NbTi matrix, and then, critical current densities have been obviously improved at higher magnetic fields. At 4.2 K, 5 T, critical current densities reached 3500 A/mm², and at 4.2 K, 8 T, it reached 1740 A/mm² for the first time. On the other hand, α-Ti particles are larger and not dispersed in Nb46.5Ti superconductors for pre-heat treated at higher temperature, and the J_c is lower, especially at low final strain. It is believed that refining the dispersed α-Ti precipitates and improving the amounts are the main reasons for improving critical current densities in Nb46.5Ti/Cu composites at higher magnetic fields.