Nb3Al conductor fabricated by DRHQ (double rapidly-heating/quenching) process

For Nb3Al compound, extremely high temperatures are required to obtain stoichiometric A15 phase, so that the rapidly-heating/quenching process have been developed. In the process the Nb/Al composite filaments change into Nb-Al supersaturated bcc solid solution filaments with rapidly-heating/quenching. The Nb-Al solid solutions are transformed into A15 phases with the post-annealing at 800 degreesC, resulting in the 2-5 times higher J(c)(4.2 K) than those of commercialized (Nb,Ti)(3)Sn wires. However, the best values of T-c=17.8 K and H-c2=26 T are rather lower than those of stoichiometric Nb3Al, which caused by its off-stoichiometry. Therefore, we tried the 2nd rapidly-heating/quenching to the 1st rapidly-heated/quenched wires having the Nb-Al solid solution filaments. The phase transformation was performed with the 2nd rapidly-heating/quenching, which is a very-short high-temperature (about 1900 degreesC) heat treatment to obtain near-stoichiometric Nb3Al, Without any additional elements, the Nb3Al compounds synthesized by the DRHQ (Double Rapidly Heating/Quenching) process show T-c and H-c2(4.2 K) of about 18.4 K and 30 T, respectively. The most interesting result is its excellent J(c)(4.2 K)-B performance, e.g., 200 A/mm(2) at 25 T, 270 A/mm(2) at 24 T and 330 A/mm(2) at 23 T.