Superconductive property and microstructure of MgB₂ particle-dispersed aluminum based composite materials

Superconducting wires have been applied for the fabrication of superconducting magnets in nuclear magneto-resonance (NMR), Magneto-resonance imaging (MRI) and so on. MgB₂ 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 MgB₂/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, MgB₂ particles dispersed to the Al matrix uniformly. The TC was determined by electrical resistivity and magnetization to be about 37 - 39K. We succeeded in extruding MgB₂/Al composite billet to 1mmφ ?wire. Microstructures of these samples have been confirmed by SEM method. MgB₂/Al composite billet and extruded wire were showed there no cracks inside the materials.