Microstructure and superconductive property of MgB₂/Al based composite materials

MgB₂ superconductingwires are interesting as the alternative conductors of Nb-based superconductingwires applied for the advanced nuclear fusion reactor because of the decay time of the induced radioactivity. However, MgB₂ is difficult for practical use because of its unworkable and lower critical current density (JC) in a high magnetic field than Nb-based superconductive materials. We have developed the original method of three-dimensional penetration casting (3DPC) to fabricate the MgB₂/Al composite materials. In the composite materials we made, MgB₂ particles dispersed in the matrix uniformly. This makes these composite materials can be processed by machining, extrusion and rolling. And the TC of the made composite materials was determined by electrical resistivity and magnetization to be 37~39K. In this work, we made composite materials with ground MgB₂ particles with the purpose of extruding thinner wires of composite material. Furthermore, we successfully produced f1mm wires and also changed the matrix from pure Al to Al-In alloy. J_C of composite materials with the matrix of Al-In alloy was calculated with the width of the magnetic hysteresis based on the Extended Bean Model. The result was better than that of MgB₂/Al composite material without Indium. Microstructures of these samples had been confirmed by SEM observation.