Superconductive Property and Microstructure of MgB_2 Particle-Dispersed Aluminum Based Composite Materials

摘要

Superconducting wires have been applied for the fabrication of superconducting magnets in nuclear magneto-resonance (NMR), Magneto-resonance imaging (MRI) and so on. MgB_2 has the highest critical temperature of superconducting transition (T_C=39K) among intermetallic compound superconductive materials. This means that MgB2 _Superconductive wire doesn't need expensive liquid He for cooling. We used the original method of the three-dimensional penetration casting (3DPC) in this laboratory to fabricate the MgB_2/Al composite. Our 3DPC method for fabricating composite materials can disperse particles in the matrix homogenously without any aggregation and control volume fractions of composites within the range of 4 - 40%, even when particle size is less than 1 μm. Thus, these composite materials can be processed by machining, extrusion and rolling. In the composite material we made, MgB_2 particles dispersed to the Al matrix uniformly. The T_C was determined by electrical resistivity and magnetization to be about 37 - 39K. We succeeded in extruding MgB_2/Al composite billet to lmmΦ wire. Microstructures of these samples have been confirmed by SEM method. MgB_2/Al composite billet and extruded wire were showed there no cracks inside the materials.