A Mössbauer spectrometry study of the kinetics of short-range ordering in FeCo

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Abstract
Making use of the systematics of 57Fe hyperfine magnetic fields (HMFs) in b.c.c. Fe-Co alloys, we have performed a Mössbauer spectrometry study of the disorder→order transformation in FeCo. Features of the 57Fe HMF distribution were used to identify: (1) the numbers of 57Fe atoms near antiphase domain boundaries, and (2) the numbers of 57Fe atoms situated on Co sites. To produce an initial state of disorder, the alloys were rapidly quenched, mostly by the piston-anvil technique. Low-temperature annealings were then used to prepare different degrees of short-range order in these materials. The number of 57Fe atoms near antiphase domain boundaries decreases more quickly with ordering than the number of 57Fe atoms situated on Co sites. This is consistent with a picture in which a dense formation of small moderately ordered domains develops very quickly, and the domains grow quickly. This is followed by an increase of order within the domains.