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Structure investigations of ferromagnetic Co‐Ni‐Al alloys obtained by powder metallurgy
Author(s) -
MAZIARZ W.,
DUTKIEWICZ J.,
LITYŃSKADOBRZYŃSKA L.,
SANTAMARTA R.,
CESARI E.
Publication year - 2010
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.2009.03263.x
Subject(s) - crystallite , materials science , ball mill , powder metallurgy , martensite , lattice constant , diffraction , powder diffraction , transmission electron microscopy , ferromagnetism , homogeneity (statistics) , solid solution , analytical chemistry (journal) , metallurgy , crystallography , microstructure , condensed matter physics , nanotechnology , chemistry , physics , statistics , mathematics , chromatography , optics
Summary Elemental powders of Co, Ni and Al in the proper amounts to obtain Co 35 Ni 40 Al 25 and Co 40 Ni 35 Al 25 nominal compositions were ball milled in a high‐energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X‐ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat‐treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered γ phase (γ’), often appearing as twins, and a small amount of the L1 0 ordered martensite.