Microstructure of the ${\rm MgB}_{2}$ Wires Resulting by the Infiltration Process

MgB₂ manufacts sintering requires a special attention in order to promote a good grain connectivity. In case of wires production, where application of pressure during sintering is practically unrealistic, the “in-situ” methods give a higher connectivity with respect to the “ex-situ” methods. In order to further improve the in-situ processing technology for the wires, we perform the Mg-RLI process, in which liquid Mg infiltration proceeds from the inner core of the wires to the surrounding B powders. The detailed microstructure analysis on the resulting MgB₂ layer of these wires shows the influence of different B powders and different operative conditions of the process, giving explanations about the relationship between powder packing density and impurity phase abundance. In particular we discuss the use, as starting precursor materials, of low-price boron powders.