Structure and distribution of chemically reactive areas have been studied on electrodeposited polycrystalline nickel having (211), (210) and (110) preferred orientations by means of electron microscopy. These characteristic preferred orientations occur in nickel specimens more than a few µ in thickness electrodeposited on mechanically polished copper substrates. Special procedures have been devised in order to directly observe the structures of thin top layers of the thick deposits having the preferred orientations by means of transmission electron microscopy.
A large number of hillocks with the ( 11) twins are formed in an electrodeposited nickel with the (211) orientation. This result was previously obtained by the author by means of reflection electron diffraction and electron microscopy using replicas, and has been confirmed in the present study. It has also been found that twin and grain boundaries in these deposits are chemically reactive and dissolved initially in a corrosive solution. In an electrodeposited nickel with the (210) orientation, twin boundaries and stacking faults are dissolved during immersion in the corrosive solution. In an electrodeposited nickel with the (110) orientation, the twinning is seldom formed, and the deposit shows no areas remarkable in chemical reactivity except grain boundaries. The electrodeposited nickel with the (211) orientation prepared by the present electrodepositing conditions appears to be more chemically reactive than the deposits having other orientations, because a high density of chemically reactive crystal defects is found in the former.
(Received July 10, 1965)
* The reseach Institute for Iron, Steel and Other Metals, Tohoku University, Sendai, Japan.
© 2002 The Japan Institute of Metals
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