19芯MgB2/NbCu/Monel超导线材的制备及性能研究

Fabrication and properties of 19-filament MgB2/NbCu/Monel superconducting wires

摘要:

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,实验中采用强度较高的梦乃尔合金(Monel 400)作为外包套材料,以原位法粉末装管工艺(in situ PIT)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Φ25 mm加工到Φ1.0 mm。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,发现多芯线材中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Φ1.0 mm的多芯线材中MgB₂超导芯丝的平均直径约为100 μm。热处理后MgB₂线材的抗拉强度和屈服强度分别达到396 MPa和200 MPa。MgB₂线材的临界电流密度在4.2 K、4 T时达到1.23×10₅ A.cm_-2。

Abstract:

For improving the mechanical properties and avoiding the filament fractures or wire breaks 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 strenth as the outer sheath materials. MgB₂ wire with the conducting structure of 19 filaments was fabricated by the PIT method. Multi-filament compound billet is processed from Φ25 mm to Φ1.4 mm in diameter with drawing, rolling and annelling process. Superconducting filament is uniformly distributed and the thickness 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 supercongducting cores is aroung 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℃/2h is around 396 MPa and 200 MPa respectively. The critical current density (Jc) is arrived 1.23×10₅ A.cm_-2 at 4.2 K、4 T.