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采用TU1无氧铜作为填充材料进行了反应堆级铌与316L不锈钢连接的真空钎焊,研究了样品和过渡接头在不同温度下的显微组织和力学性能.显微组织表明形成了脆的金属间化合物层并观察到结合面有扩散现象发生.虽然在结合面有脆性金属间化合物形成,但并不影响其在超导射频(SRF)腔中的使用.在室温(300 K)和液氮温度(77K)下进行了拉伸测试和剪切测试.在液氮温度下,抗张强度高于其在室温下的抗张强度,由于脆性金属间化合物的存在导致其在液氮环境下抗剪切强度低于室温环境.由于我们严格控制焊缝厚度,使过渡接头的抗剪切强度高于样品的强度.最后我们对过渡接头进行真空漏率测试.结果 显示,其真空漏率均低于1.1×10-9Pa·L/s,这表明真空钎焊技术适用于低温下使用的高真空容器,例如用于SRF腔的不锈钢氦容器.“,”A vacuum brazing technique was used to braze reactor grade niobium and 316L stainless steel with oxygen-free copper as filler materials.Microstructure and mechanical properties of both samples and transition joints at different temperatures were investigated.Results demonstrate that brittle intermetallic layer forms and diffusion phenomenon is observed.In spite of the existence of brittle intermetallic,the brazing joints' application in superconducting radio frequency (SRF) cavities is not affected.Mechanical tests including tensile tests and shear tests were conducted both at room temperature (300 K) and liquid nitrogen temperature (77 K).The tensile strengths at liquid nitrogen temperature are higher than at room temperature,while the shear strengths are reduced due to the formation of brittle intermetallic.The transition joints always have higher mechanical strengths than samples when the thickness of the brazing seam is strictly controlled.Leak tests were also performed on the transition joints.The joints' leak rates are all lower than 1.1×109 Pa·L/s,indicating that the vacuum brazing technology is applicable to high vacuum vessels used at cryogenic temperatures,such as stainless steel helium vessel for SRF cavities.