Electron Microscopy Study of Hypostoichiometric Fe-Pd Nanocomposites Resulting from Combined Reactions Thermomechanical Processing
Hypostoichiometric Fe-Pd binary alloys (35-45 at% Pd) were severely deformed (>90%) and subsequently aged to induce concomitant recrystallization, precipitation, and ordering. This thermomechanical processing strategy was articulated by Hornbogen  over thirty years ago. The resulting exchange-coupled ferromagnets contain ferrite precipitates and a complex metastable two-phase lamellar transformation product comprised of ordered L10 and a metastable FCC phase. The later duplex microconstituent is suggested to form in conjunction with a so-called pseudospinodal reaction  involving emerging cubic and tetragonal phases, whereby phase separation and ordering result from continuous changes in composition and a reduction in symmetry, cubic to tetragonal. The deformation texture of the parent austenite is substantially retained in the transformation product, resulting in anisotropy of the magnetic properties as determined by magnetometry (VSM). This paper presents electron microscopy results elucidating the crystallography and morphology of the phase mixtures including HREM. Magnetic field annealing is also included as a branch of our thermomechanical processing strategy, and we discuss the influence of the external fields on recrystallization, precipitation, and ordering.
Yves Bréchet, Emmanuel Clouet, Alexis Deschamps, Alphonse Finel and Frédéric Soisson
E. D. Cantando et al., "Electron Microscopy Study of Hypostoichiometric Fe-Pd Nanocomposites Resulting from Combined Reactions Thermomechanical Processing", Solid State Phenomena, Vols. 172-174, pp. 356-361, 2011