Coupling magnetic-thermal field effect on precipitation kinetics of Al–Cu–Mg alloy investigated by SAXS and WAXS

The effect of a stable magnetic field (1 T) on precipitation kinetics in an Al–Cu–Mg alloy (AA2024) aged at different temperatures has been systematically studied by small angle X-ray scattering (SAXS), transmission electron microscope (TEM) and wide angle X-ray scattering (WAXS). The synchrotron SAXS and WAXS results reveal that the precipitation kinetics in different scales is facilitated by magnetic field at ageing process. Based on the WAXS findings, under the magnetic field, the precipitation of CuAl₂Mg, Al₇Cu₂Fe and CuAl₂ phases is accelerated at all ageing process, and the highest enhancement of relative intensity of them reaches 262%. Among them, at low ageing temperature (at 130 °C), the percentage of relative intensity of CuAl₂Mg and Al₇Cu₂Fe phases between with and without magnetic field are increased by 48%–120% and 93%–257%, respectively, as compared to the values 1 of above two phases observed at other ageing temperature (at 160–240 °C). Modifications of the precipitation kinetics under magnetic field could be associated with two reasons. One is solute diffusion increase, this is attributed to the increase of solute diffusion coefficient, which results from the change of frequency factor of atom caused by magnetic field. Another is critical nucleation energy decrease and critical nucleation rate increase, which is attributed to the presence of magnetic field energy under magnetic field.