Abstract
Lattice imaging provides direct evidence to support the existence of solute-atom clusters on {001} matrix planes in α-iron. Nitrogen and manganese-nitrogen atom clusters (GP zones) are shown to precede the formation of the intermediate precipitates α″-Fe16N2 and η-Mn3N2 in nitrogen-ferrite and an Fe-2·17 at.% Mn-1.3 at.% N alloy, respectively. The manganese-nitrogen zones form as flat platelets analogous to those observed in Al-Cu alloys. However, nitrogen GP zones form with a complex undulating platelet morphology which is retained during the continuous transition to the α″-Fe16N2 precipitate.
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