Axial Tensile Stress–Strain Characterization of Bi-2212 Round Wire With Different Heat Treatments

The China Fusion Engineering Test Reactor is a new tokamak device whose magnet system includes toroidal field (TF), central solenoid (CS), and poloidal field (PF) coils which are made up of cable-in-conduit conductor (CICC). The maximum field of CS and TF will reach around 15 T, which is much higher than that of present reactors. In this case, the high-temperature superconducting material Bi-2212 is considered as one potential magnet material for CICC because it has an outstanding conductor-carrying capacity at 4.2 K in magnetic field, especially for that with high-pressure heat treatment. However, Bi-2212 phase is a ceramic structure, which is sensitive to strain. The mechanical property is important for its application. In this paper, the axial tensile measurements on Bi-2212 round wires with different heat treatments were performed at room temperature, 77 K and 4.2 K, respectively. It was found that the wires with high pressure heat treatment had higher mechanical strength than that with normal pressure. The compared results were given, and SEM of cross sections for tested samples was also made and analyzed.