Electron diffraction study of aging processes in Fe-1.83 Wt Pct C martensite at room temperature

Aging processes occurring in an Fe-1.83 wt pct C martensite at room temperature have been studied by electron diffraction, assisted by transmission electron microscopy observation. Fourier analysis of diffuse scattering from the martensite suggested that a spinodal decomposition occurred therein. The spinodally modulated microstructure was composed of a dominant wave with a wavelength of about 1 nm and nondominant waves with longer wavelengths and was observed not to grow even after aging for several months. The reason for the nongrowth may be that the coarsening was stopped by strong elastic interactions between carbon-enriched and carbon-depleted regions. Furthermore, the tetragonality of the martensite was observed to remain constant during aging, suggesting that carbon redistribution during spinodal decomposition occurred within one set of the octahedral interstitial sites O{sub z} only.