In magnet applications using REBa ₂ Cu ₃ O _y (RE = rare earth, Y, Gd, etc., REBCO) coated conductors, micro-cracks caused by mechanical slitting are one of the most worrisome phenomena because they could be the origin of critical current degradation. In this study, we have investigated the crack formation caused by twisting the REBCO tape by using scanning Hall-probe microscopy (SHPM) and scanning electron microscope (SEM). First, twist, the most severe load on the crack, was applied to the 4 mm-wide REBCO tape divided by mechanical slitting, and the variation of critical current with the torsion angles was investigated. Then, magnetization distribution measured by SHPM revealed that these decreases in critical current correspond to crack formation. The micro-cracks introduced initially during the slitting process are not the origin of the crack formation that spread throughout the tape. On the other hand, for the REBCO tape after the irreversible twist test, additional cracks have also been confirmed even though the critical current has not yet decreased.

中文翻译：

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使用扫描霍尔探针显微镜观察 REBCO 涂层导体扭曲形成的裂纹

在使用 REBa ₂ Cu ₃ O _y（RE = 稀土、Y、Gd 等，REBCO）涂层导体的磁体应用中，机械切割引起的微裂纹是最令人担忧的现象之一，因为它们可能是临界裂纹的根源。当前的退化。在这项研究中，我们使用扫描霍尔探针显微镜 (SHPM) 和扫描电子显微镜 (SEM) 研究了 REBCO 胶带扭曲引起的裂纹形成。首先，将裂纹上最严重的载荷扭转施加到通过机械切割分割的4毫米宽的REBCO带上，并研究临界电流随扭转角的变化。然后，SHPM 测量的磁化分布表明，临界电流的这些降低对应于裂纹的形成。在分切过程中最初引入的微裂纹并不是在整个胶带上扩展的裂纹形成的根源。另一方面，对于不可逆扭曲测试后的REBCO带，即使临界电流尚未降低，也确认了额外的裂纹。