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采用粉末装管法(PIT)已经可以制备出千米量级Mg B2超导长线,但依然没有完全满足应用需求,如何继续提高线材的单根长度仍然是Mg B2超导材料研究领域的一个重要方向。在传统的原位PIT法制备Mg B2超导线材的过程中,引入挤压工艺对其进行加工处理。分别用Cu和Cu-Nb作为中心增强材料,组装两个37芯Mg B2包套,通过挤压、拉拔工艺对其进行加工处理。采用金相显微镜(OM)和扫描电子显微镜(SEM)对线材截面和断口的微观形貌进行分析,采用1μV?cm-1的电压判据和标准四引线法测量样品在4.2K下的Ic(B)曲线,得出样品在该温度下的Jc(B)曲线。结果发现挤压过程所有组元变形基本同步,挤压工艺有效地增加了芯丝致密度。制备的直径3.0 mm Cu芯线材在4T,4.2K下Jc达到2.48×104A?cm-2;Cu-Nb芯线材在4T,4.2K下Jc达到1.59×104A?cm-2。采用挤压工艺加工Mg B2复合包套的途径是可行的,但挤压过程中复合体一次变形量超过90%,目前采用的导体结构需要进一步优化,将有助于提高所制备线材的长度和性能。
It has been possible to prepare the Mg2.2 superconducting wire of kilometer-size by powder tube method (PIT), but still not fully meet the application requirements. How to continue to increase the single length of the wire is still an important area of research in MgB2 superconducting materials direction. In the process of preparing MgB2 superconducting wire by the traditional in-situ PIT method, it is processed by extrusion process. Cu and Cu-Nb were used as the center reinforcing material respectively, and two 37-core Mg B2 sheaths were assembled and processed by extrusion and drawing processes. The micrographs of the cross section and the fracture surface of the wire were analyzed by OM and SEM. The voltage of 1μV? Cm-1 and the standard four-lead method were used to measure the Ic B) curve to obtain the Jc (B) curve of the sample at this temperature. The results show that the deformation of all the components in the extrusion process is basically synchronous, and the extrusion process effectively increases the density of the core filaments. The Jc diameter of 3.0 mm Cu core wire prepared at 4T and 4.2K reaches 2.48 × 104A cm-2. The Jc of Cu-Nb core wire reaches 1.59 × 104A cm-2 at 4T and 4.2K. It is feasible to use the extrusion process to process the MgB2 composite sheath. However, once the deformation amount of the composite exceeds 90% during the extrusion, the current conductor structure needs to be further optimized, which will help to improve the length and performance.