9 Mössbauer Spectroscopic Studies on Atomic Diffusion in Materials
509
Fig. 9.62 (a) Mössbauer spectra after the annealing from 100 to 700 °C, and (b) their successive
subtractions [from Ref. 98]
subtractions indicate clearly that the first segregation of carbon atoms appears to start
after the annealing 100 °C. The overall phase separation from martensite to ferrite
+ cementite occurs at 400 °C, which is accompanied by the transformation from
“retained austenite” to “ferrite” phases.
Figure 9.63 summarizes the MSM electron and γ-ray images of the Fe steel for
the annealing at 100, 200, 400 and 700 °C as well as the spectral components of
Ferrite, Austenite, 1st NN Fe of O-site Carbon in Ferrite, and Cementite. Since we
measured five different samples after quenching and annealing at high temperatures,
you could compare the contour maps for the different components. Although the
present sample contains many components, we obtained the mapping images separately for the different components by tuning to the 1–6 lines among all the sextet. In a
ferromagnetic sample, however, we have to consider magnetic domains by measuring
all six lines to get the concentration distributions of the different phases. To study the
carbon diffusion in the microstructure of martensite and austenite phases, we have
to investigate one sample either after isochronal annealing at high temperatures, or
509
Fig. 9.62 (a) Mössbauer spectra after the annealing from 100 to 700 °C, and (b) their successive
subtractions [from Ref. 98]
subtractions indicate clearly that the first segregation of carbon atoms appears to start
after the annealing 100 °C. The overall phase separation from martensite to ferrite
+ cementite occurs at 400 °C, which is accompanied by the transformation from
“retained austenite” to “ferrite” phases.
Figure 9.63 summarizes the MSM electron and γ-ray images of the Fe steel for
the annealing at 100, 200, 400 and 700 °C as well as the spectral components of
Ferrite, Austenite, 1st NN Fe of O-site Carbon in Ferrite, and Cementite. Since we
measured five different samples after quenching and annealing at high temperatures,
you could compare the contour maps for the different components. Although the
present sample contains many components, we obtained the mapping images separately for the different components by tuning to the 1–6 lines among all the sextet. In a
ferromagnetic sample, however, we have to consider magnetic domains by measuring
all six lines to get the concentration distributions of the different phases. To study the
carbon diffusion in the microstructure of martensite and austenite phases, we have
to investigate one sample either after isochronal annealing at high temperatures, or