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Description
Chinese Fusion Engineering Test Reactor (CFETR) is considered to be one of the most ambitious fusion energy projects capable of producing large-scale nuclear fusion reactions, whose superconducting magnet system consists of the toroidal field (TF) coils, central solenoid (CS) coils and poloidal field (PF) coils. The modified N50 austenitic stainless steel has been determined to be applied as the jacket material of the CICCs (Cable-In-Conduit Conductors) of both the TF coils and the CS coils and the case material of the TF coils in the CFETR, which would undergo a series of pre-deformation during the manufacture process at room temperature. It is proved that mechanical properties of the modified N50 could meet the service requirements of future conductors of the CFETR, however, the knowledge of effect of pre-strain on cryogenic mechanical properties of the modified N50 is limited. In order to investigate the influence of tensile pre-strain at room temperature on cryogenic tensile properties, especially the yield strength (Rp0.2), ultimate tensile strength (Rm), elongation at fracture (A), and the microhardness (HV0.3) of the modified N50 with different tensile pre-straining amounts of 0%, 15%, 25%, and 35% were measured at room temperature (300K), liquid nitrogen temperature (77 K), and liquid helium temperature (4.2 K), respectively. Moreover, the microstructure evolution of the modified N50 was investigated through the scanning electronic microscopy (SEM) and the transmission electronic microscopy (TEM), which would indicate fractured morphologies and also dislocation accumulations of the pre-strained modified N50. In addition, the strain hardening behavior of the modified N50 was compared with that of the ITER-grade 316LN. This work would provide more reliable mechanical data of the modified N50 in cryogenics applications.
| Submitters Country | China |
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