Observation of A15 phase transformation in RHQ-Nb3Al wire by neutron diffraction at high-temperature

► A15 phase transition from solid solution occurred within 5 min in RHQ-Nb3Al wire. ► The holding duration of 9 h at 800 °C was found to optimize growth of the A15 phase. ► The residual strain in the Nb3Al filaments appeared between 200 and 300 °C. ► An isotropic tensile strain of 0.07% was found in the Nb3Al at room temperature. ► The tensile effect of the Nb/Ta matrix was dominant in the RHQ-Nb3Al wire.