Equiaxial nano-crystals Nb3Al superconductor prepared by optimized mechanically alloying
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The influence of the original nominal chemical composition, milling time, sintering temperature and holding time was studied systematically on the phase formation, microstructure and superconductivity of mechanically alloyed Nb3Al. By optimizing the process, we have successfully prepared high-performance Nb3Al superconductor. Samples with original nominal composition of Nb-27 at.%Al were milled for 3 h and sintered at 900 °C for 1 h, resulting in an entire A15 superconducting phase, except a few negligible Nb2Al phase. The superconducting critical transition temperature (Tc) and the upper critical field at absolute zero (Hc2(0)) reached 15.7 K and 28.1 T, respectively. It should be noted that the superconducting critical current density (Jc) was still as high as 6.3 × 104 A cm−2 at a temperature of 4.2 K under an applied magnetic field of 7 T, as well as a maximum flux pinning force (Fp,max) of 6.23 × 109 N m−3 in the whole magnetic field range at 4.2 K. All of the results could be attributed to the microstructure of the sample with equiaxial nano-crystals.
The authors are grateful for the financial support of the National Key Research and Development Plan (Grant No. 2017YFE0301401), Sichuan Province Science Program (Grant Nos. 2017JY0057, 2018JY0003), the National Natural Science Foundation of China (Grant Nos. 51702266, 51271155, 51302224, 51377138) and the Program of International S&T Cooperation (Grant No. 2013DFA51050).
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