19芯MgB2/Nb Cu/Monel超导线材的制备及其性能

Fabrication and Properties of 19-Filament MgB2/NbCu/Monel Superconducting Wires

为了提高多芯MgB2超导线材的强度并避免加工过程中的断芯、断线现象,采用强度较高的梦乃尔合金(Monel400)作为外包套材料,以原位法粉末装管工艺(insituPIT)制备了19芯导体结构的多芯MgB2超导线材。二次集束组装后的多芯复合线材通过拉拔、轧制和中间退火热处理相结合的方法从Φ25mm加工到Φ1.0mm。对加工过程不同阶段的多芯复合线材进行了微观结构分析。结果表明,多芯线材中MgB2芯丝分布较为规整,Nb阻隔层表面较为光滑,未出现明显破损现象。最终Φ1.0mm的多芯线材中MgB2超导芯丝的平均直径约为100μm。热处理后MgB2线材的抗拉强度和屈服强度分别达到396和200 MPa。MgB2线材的临界电流密度在4.2 K、4 T时达到1.23×10^5 A·cm^-2。

To improve the mechanical properties and to avoid the filament fracture or wire breaking in multi filament MgB2 wire,the traditional in-situ powder in tube(PIT) method was introduced to the MgB2 wires fabrication process using the Monel alloys with higher strength as the outer sheath materials.Then the MgB2 wire with the conducting structure of 19 filaments was fabricated by the PIT method.Multi-filament compound billet was processed from Φ25 mm to Φ1.0 mm in diameter with drawing,rolling and annealing process.The results show that superconducting filament is uniformly distributed and the surface of Nb diffusion barrier is also smooth without breaking points through the microstructure analysis of the wires at each fabrication stages.The mean diameter in MgB2 superconducting cores is around 100 μm in final wires with the diameter of Φ1.0 mm.The tensile strength and yield strength of the wire heat-treated at 670 ℃/2 h is around 396 and 200 MPa,respectively.The critical current density(Jc) reaches 1.23×10^5 A·cm^-2 at 4.2 K,4 T.