Fabrication of high-entropy alloy superconducting wires by powder-in-tube method

Abstract

High-entropy alloys (HEAs) are novel functional materials that exhibit excellent mechanical and chemical properties. Recent discovery of self-healing superconductivity of HEAs under ion irradiation suggests their great potential applications under extreme conditions such as in nuclear fusion reactors or space environments. Here, we report a fabrication of the HEA superconducting (SC) wires using the ex-situ powder-in-tube (PIT) technique for the first time, a crucial stepping stone to achieve various industrial and technological applications. The Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 HEA SC powder prepared by planetary ball milling was filled into Fe tubes, drawn into wires, and then sintered in evacuated quartz tubes at various temperatures. The HEA SC wire sintered at 700 °C for 1 h exhibits the highest critical current density (Jc) among the HEA SC wires sintered in the temperature range of 600 – 1000 °C. At 4.2 K, the Jc of this wire exceeds the common benchmark value of Jc = 100 kA cm−2, indicating the suitability of the HEA wire for large-scale applications, such as in high-field SC magnets. The SC transition temperature (Tc) of the HEA wire significantly increases from 5.10 K for the as-cast wire to 7.58 K with the sintering time (ts) of 30 min at 700 °C. The scaling of the flux pinning force as a function of the magnetic field indicates that normal point pinning plays a major role in achieving a high in-field Jc in HEA SC wires. These results underscore the significant potential of HEA superconductors for practical applications in high-field SC magnets, SC electric machines, and next-generation nuclear fusion reactors.