Martensitic transformation in FePd alloy revealed by synchrotron radiation

Synchrotron radiation experiments were performed for the precursor study of the martensitic transformation in Fe68.6Pd31.2 (numbers indicate at.%) alloy. Tunable wavelength is one of advantages of synchrotron radiation and was utilized in the present work. Six wavelengths, which give various penetration depths and give information from various depths, were chosen for observing the transformation behavior. Oscillation photographs with various wavelengths were taken at several temperatures above the martensitic transformation temperature. Those oscillation photographs showed splitting of Bragg reflections and 〈1 1 0〉 diffuse streaks and also showed a wavelength dependence. Thus the transformation mechanism was discussed from a viewpoint of precursor phenomenon and incomplete phonon softening features.