Neutron diffraction and phase evolution of the mechanically alloyed intermetallic compound zeta-FeZn13

High-energy ball milling with subsequent annealing is used to synthesize th e intermetallic compound zeta -FeZn13. The mechanically alloyed phase in th e as-milled state is determined to be nonequilibrium, or metastable. Transm ission electron microscopy (TEM) studies show a highly defective microstruc ture with undefined grain areas, and the alloy can be described as a mechan ical mixture of elemental Fe and Zn, based on neutron diffraction measureme nts. Characteristic stages associated with its transformation to the equili brium state are identified based on differential scanning calorimetry (DSC) measurements. The activation energies corresponding to these stages are 12 8, 202, and 737 kJ/mole, respectively, with increasing transformation tempe ratures. The first stage is related to limited atomic diffusion or rearrang ements, such as recovery, during thermal treatment, while the second stage depicts continued recrystallization and long-range atomic diffusion leading to a stable phase formation. The third and final stage marks structural de composition of the equilibrium structure due to phase transition. Neutron d iffraction of the equilibrium alloy confirmed that the structure is C2/m, w ith lattice parameters of a = 13.40995 Angstrom, b = 7.60586 Angstrom, c = 5.07629 Angstrom, and beta = 127 deg 18 minutes. The atomic positions of Fe and Zn compared well to reported values.