Improvement of Jc by cold high pressure densification of binary, 18-filament in situ MgB2 wires

Cold high pressure densification (CHPD) has recently been found to be a promising way to improve the critical current density, J, in single-core MgB wires prepared by insitu processing. In this work, the CHPD process was also applied to multifilamentary, binary MgB wires, leading again to a strong enhancement of the transport J. The fields and where the transport J at 4.2K reaches the value 1 × 10Acm for parallel and perpendicular fields were determined as 8.5 and 8.2T, respectively (0.1 νVcm criterion). The behaviour of J versus B at 20 and 25K was almost isotropic, the corresponding values being 4.7 and 3T, respectively. The observed enhancement of J by a factor 2.3 at 4.2K at all applied fields up to 10T in densified samples is directly correlated with the observed enhancement of the mass density and microhardness. The decrease of the electrical resistivity of the densified wire reflects improved grain connectivity in the filaments. The improvement of J by CHPD was still observed after sequential pressing with overlapping regions, up to a total wire length of 150mm. This result is promising as regards practical applications