X-Ray Micro-Tomography as a Tool for Quantitative Characterization of Advanced Materials Manufacturing Processes

Abstract

The potential of X-ray micro-tomography in characterizing the relevant material issues as identified during manufacturing processes was investigated. For this purpose, the 3D X-ray micro-tomography (XµRT) analysis was applied to the characterization of structural integrity of Nb3Sn superconducting wires of differing topology and the evolution of the density distribution of ceramic samples manufactured by Field Assisted Sintering Techniques (FAST). The latter technique was used to consolidate the ceramic, metal (Ni) and composite powders (MgB2). The usual scanning electron microscope (SEM) technique was enhanced by the high resolution XµRT in order to describe the volumetric density distribution before sintering and at different moments of the thermal cycle. Two types of samples sintered Ni and high density MgB2 superconductors with typical volume of 0.8÷1.5⋅10-9 m3 were sampled at space resolution around 5µm. For the sintered Ni, the 3D reconstructed volumes revealed the grain connectivity, necks formation and particle rearrangement in the densification process. The XµRT analysis was essential in explaining the differences in superconducting properties of MgB2 samples in terms of different volumetric structures. For the Nb3Sn multifilamentary wire which is at basis of many practical superconductors, the 3D tomography enabled the determination of the number of inter-filament contacts as well as the twist-pitch parameter. Advantages of our method versus the invasive etching techniques for the determination of the twist-pitch parameter were outlined.