A comprehensive analysis of MgB2 superconducting wire development: The effect of initial filling density and thermomechanical treatment

This research explores the modern fabrication of MgB2 superconducting wire through an advanced hot rolling process with a stainless-steel sheath. This study aims to analyze the effect of variations in the filling density of powders in the tubes on the phase transformation, microstructure, superconductivity, current density, and hardness values in the fabrication of MgB2-based superconducting wire. The superconducting wire was produced using powder metallurgy in the powder-in-tube process and wire bundles were produced by hot rolling. Subsequently, hot rolling was performed to reduce the outer diameter size from 8 mm to 2.8 mm, and the initial length from 11 cm to ± 40 cm. The XRD results show that each sample produces the main phase MgB2 and some impurities (Mg and MgO), with the crystallite size decreasing as the percent infill density decreases. From the FESEM image, the sample shows fewer voids and becomes homogeneous. The sample with 80 % filling density is the optimal density for powder filling in the MgB2 superconducting tube, exhibiting the highest critical temperature onset of 39.25 K. This sample also produces the maximum critical current density, 30 A/cm2 (2T).