Properties of hydrostatically extruded in situ MgB2 wires doped with SiC

In situ nano-SiC doped MgB2, wires were fabricated from MgH2 and B powders. Hydrostatic extrusion, followed by rotary swaging and two-axial rolling, were applied as the forming processes. The critical current J(c), of MgB2, wires, made from MgH2 and B powders, was significantly improved by nano-SiC doping. Nano-SiC doping substantially increased the upper critical (irreversibility) field B-c2 above 20 T. The maximum J(c) values were measured for samples having 6 at.% SiC in low field and for those having 12 at.% SiC In high field, above 10 T. During the final sintering at 670 degrees C, the SiC decomposed and formed an Si-rich layer at the inner circumference of the Fe sheath. The composition of the core of SiC doped wires is more inhomogeneous in comparison to undoped ones, with MgO, Mg2Si and probably Mg2SiO4 as the major segregated phases. Strong segregation of Si within the MgB2 core was also observed. The highest T-c-mid = 39.3 K was measured for undoped wire. For the optimal SiC doping amount similar to 6 at.%, at high field, there was no difference in J(c) between hydrostatically extruded and hydrostatically extruded plus two-axially rolled wire. This can be attributed to the beneficial effect of hydrostatic extrusion, which causes higher density of the core in comparison to traditional deformation processes.