Advanced MgB2 wire made by internal magnesium diffusion process.

Highlights: [•] Single- and four-core MgB2 wires have been manufactured by internal magnesium diffusion (IMD) into boron. [•] High density of MgB2 was evaluated by micro-hardness measurements. [•] The critical current densities of IMD wires are 17 times higher in comparison to those made by powder-in-tube process. [•] High current densities of IMD wires are promising for practical applications of MgB2. [ABSTRACT FROM AUTHOR]