Electromechanical Performance Study on Silver Diffusion Joints of REBCO Coated Conductors under Axial Tensile Stress

Abstract

Silver diffusion method is a promising candidate for joining the second generation high temperature superconducting tapes that can achieve a joint resistance of nΩ level while retaining full critical current. In this study, silver diffusion joints with joint resistance as low as <; 2 nΩ was demonstrated. The performance of silver diffusion joints under axial tension load, which is considered as a key parameter for their practical applications, was also systematically studied. It was investigated that the nominal critical axial tensile stress of the unlaminated silver diffusion joint fabricated by the coated conductor tapes from Shanghai Superconductor Co., Ltd. was in the range of 430-480 MPa, which is significantly lower than that of the single tape (approximately 590 MPa) and could hardly be improved by increasing the overlap length from 1 to 10 cm or by modifying the configuration from the lap-type to the enhanced bridge-type. According to the experimental results, the failure mechanism of silver diffusion joints under tensile stress was discussed. Based on which, a post-lamination process was proposed to alleviate the local stress concentration. The laminated silver diffusion and single straight tape exhibited consistent behavior under axial tension load and, therefore, the same critical axial tensile stress.