Effect of the Design on the Mechanical Properties of Internal-Tin Nb 3 Sn Superconducting Strand

Compared with the bronze process, Nb3Sn strands prepared by the internal-tin (IT) process have higher Sn contents and can generate more Nb3Sn phases, making it the main method for preparing Nb3Sn strands with high critical current density. The Nb3Sn phase formed after heat treatment is a brittle intermetallic compound, and the filament damage and performance degradation under low-temperature and high-magnetic-field conditions need attention. During use, the compression and tensile strains on the strand can lead to performance attenuation. Therefore, it is important to study the relationship between performance degradation and the preparation process for the practical application of the strand. By optimizing the strand design and heat treatments, we prepared Nb3Sn strands with different mechanical properties. The critical current densities under different magnetic fields were tested. The internal local strain of the filaments was analyzed, and the relationship between heat treatments, and the mechanical properties of the strand were improved, enhancing its engineering application prospects.