Tao Jia, Wu Jiefeng, Liu Zhihong, Ma Jianguo, Liu Zhenfei, Peng Wuqingliang
Institute of Plasma Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China.
Science Island Branch, University of Science and Technology of China, Hefei 230026, China.
Materials (Basel). 2022 May 25;15(11):3778. doi: 10.3390/ma15113778.
The electron beam welding of the tubes and the half-cells for our 1.3 GHz single-cell superconducting radiofrequency (SRF) cavities is complex due to the different thicknesses of the tubes and the half-cells in the iris region. However, the mechanical properties and microstructure of the iris welds in niobium SRF cavities have barely been explored in previous studies. For high-quality iris welds, welding experiments of niobium sheets of 2 mm and 2.8 mm were carried out under different oscillating conditions. The results show that welding with no oscillation or sinusoidal oscillation may not be applied in actual welding owing to the large misalignment of the bottom surface. The weld grains were not significantly refined through beam oscillation. The joints with infinity oscillation had a higher elongation than circular oscillation, which exhibited a brittle fracture in the tensile tests at 77 K. Nevertheless, the texture of the weld with infinity oscillation implies poor formability, so the feasibility of infinity oscillation in actual welding needs verification in future study.
对于我们的1.3吉赫兹单腔超导射频（SRF）腔，由于管和半腔在虹膜区域的厚度不同，管与半腔的电子束焊接很复杂。然而，此前的研究几乎未对铌SRF腔中虹膜焊缝的力学性能和微观结构进行探索。为了获得高质量的虹膜焊缝，对2毫米和2.8毫米厚的铌板在不同振动条件下进行了焊接实验。结果表明，由于底面的较大错位，无振动或正弦振动焊接可能不适用于实际焊接。通过束流振动，焊缝晶粒未得到显著细化。无限振动接头的伸长率高于圆周振动接头，后者在77K拉伸试验中呈现脆性断裂。然而，无限振动焊缝的织构意味着可成形性较差，因此无限振动在实际焊接中的可行性有待未来研究验证。
