Fabrication of extruded wire of MgB₂/Al composite material and its superconducting property and microstructure

Superconductive MgB₂/Al composite material with low and high volume fractions of particles were fabricated by our special pre-packing technique and 3-dimensional penetration casting (3DPC) method. The composite material showed homogeneous distribution of MgB₂ particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (T _C) was determined by electrical resistivity and magnetization to be about 37 ∼ 39K. A billet of the superconducting composite material was successfully hot-extruded, forming a rod of 10 mm and wires of 3 and 1 mm in diameter. These intermediate products showed the onset T_C of electrical resistivity also at 37-39 K. Microstructures of these samples have been observed by TEM and SEM method to establish morphology and crystallography of particles. The magneto-optic (MO) imaging method has been also applied to measure magnetic flux through this composite material when in external field.