High magnetic field effects on the phase separation behaviour of Fe-15mass%Cu alloys probed by ⁵⁷Fe Mössbauer spectroscopy

High magnetic field effects on the phase separation of Fe-rich and Cu-rich phases in Fe-15mass%Cu were investigated using microstructural observation and ⁵⁷Fe Mössbauer spectroscopy. Fe-15mass%Cu annealing was carried out at 773 K with or without a 5 T magnetic field. Microstructural observations showed that the Fe-rich grains were separated by a Cu-rich phase, and the width of the Cu-rich phase for the samples annealed at 5 T tended to be narrower than that of the samples annealed at 0 T. The Mössbauer spectrum of the samples measured at room temperature is represented by two sub-spectra. The hyperfine fields B_hf of the two sub-spectra were 33.0–33.1 T and 31.4–31.7 T and they did not change with annealing time or the presence of a magnetic field. The spectrum with a higher (lower) B_hf corresponded to the centre (near the grain boundary) of the Fe-rich grain. The occupancy of the spectrum with a lower B_hf for the sample annealed at 5 T was larger than that for the sample annealed at 0 T by up to 5%. This indicated that the change of Cu concentration at the grain boundary became gentle. Therefore, the high magnetic field effects were coarsening of the Fe-rich grains and a gentle change in the Cu concentration at the grain boundary.