Viewpoint on fast creation of dense MgB2 phase in wires made by internal Mg diffusion process

Abstract

Md Shahriar Al Hossain, University of Wollongong, shares his views on a letter by P KovaAcA○ and colleagues on fast creation of dense MgB phase in wires made by internal Mg diffusion process. According to him, In situ and ex situ powder metallurgical processes are currently used for the industrial fabrication of mono- and multi-filamentary MgB wires. The mass density in the MgB filaments of the wires after the final heat treatment is quite low with respect to the theoretical density. The typical effective superconductor area in the wire is only about 10%. Cold high pressure densification (CHPD) has been suggested as an alternative to enhance filament mass density. The authors showed that 8 min sintering time is sufficient for the formation of a uniform MgB2 phase 90 μm in thickness and without cracks, which is nearly identical to samples produced under the same sintering temperature conditions but longer sintering time of 3?5 h that were previously reported by the NIMS group. This finding is important for economical industrial production, but a question still remains as to how the round wires with a hollow filament will perform in magnet design and application, where enhancement of the filling factor, reduction of filament size, and mechanical and electrical stability and reliability are key factors.