Fabrication of Nb3Al superconducting bulks by mechanical alloying method

Abstract Since it can directly prepare the Nb–Al supersaturated solid solution, mechanical alloying is thought as a promising method to make high-performance Nb 3 Al superconductors at a low temperature annealing condition, without the complicated rapid heating, quenching and transformation (RHQT) process. In this paper, we investigate the effects of milling time, the content of Al and annealing temperature on phase formation and superconducting properties of mechanical alloying Nb 3 Al bulks in detail. The study results show that Nb–Al supersaturated solid solution could be obtained by high energy ball milling, as long as the Nb–Al blended powder is ball milled for 1 h, even the amorphous phase appears with the ball milling time prolonging to 10 h, the Nb–Al intermetalics do not come out either. Amorphous phase is hardly beneficial to synthesizing the Nb 3 Al phase, instead, it will make the products impurity. By optimizing the milling time, elements composition and annealing temperature , pure Nb 3 Al phase is obtained and the highest onset superconducting transition temperature ( T c-onset ) reaches 15.8 K and the critical current density ( J c ) 10 6  A/cm 2 at 8 K without outer field. This paper also discusses the main reasons that affect the superconducting properties of mechanical alloying Nb 3 Al superconductor.