Microstructure and superconductive property of MgB₂/Al composite materials

MgB₂ has the higher critical temperature of superconducting transition (T_C : 39K) among the intermetallic compound superconductive materials, however, MgB₂ is hard for practical use because of its unworkable and lower critical current density (J_C) 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 material we made, MgB2 particles dispersed to the matrix uniformly. Thus, these composite materials can be processed by machining, extrusion and rolling. The T _C was determined by electrical resistivity and magnetization to be about 37∼39K. In this work, we made composite material with ground MgB ₂ particle with the purpose of extruding thinner wires of composite material, successfully produced φ1mm wire and changed the matrix from pure Al to Al-In alloy. J_C of composite materials with the matrix of Al-In alloy was calculated from 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.