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Microstructure characterization of ball‐milled Ni 50 Co 50 alloy by Rietveld method
Author(s) -
Loudjani Nadia,
Bensebaa Nadia,
Alleg Safia,
Djebbari Chaffia,
Greneche Jean Marc
Publication year - 2011
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201026723
Subject(s) - materials science , crystallite , rietveld refinement , ball mill , microstructure , lattice constant , solid solution , crystallography , scanning electron microscope , alloy , dissolution , crystal structure , metallurgy , analytical chemistry (journal) , chemical engineering , diffraction , composite material , chemistry , physics , chromatography , optics , engineering
A nanostructured Ni 50 Co 50 mixture was prepared by high‐energy ball milling in a planetary ball mill (Frisch P7) under an argon atmosphere. Scanning electron microscopy and X‐ray diffraction (XRD) have been used to study the morphology of the powder particles, microstructure, and structure evolution. Detailed analysis of the XRD patterns was performed by the MAUD program, which is based on the Rietveld method. It reveals the complete vanishing of the Co peaks after 3 h of milling, indicating the allotropic transformation of Co from hcp to fcc structure. The reciprocal dissolution of the elemental Ni and Co powders leads to the formation of a heterogeneous solid solution with two structures: fcc‐Ni(Co) and fcc‐Co(Ni) with relative fractions of about 76 and 20%, respectively, after 24 h of milling. Microstructural parameters such as lattice parameter, crystallite size, microstrains, dislocation density, and stacking faults have been deduced from the best Rietveld refinements. The formation kinetics of nanostructured Ni 50 Co 50 mixture can be described by a lower Avrami parameter, n, close to 0.34.