STATISTICAL ANALYSIS OF AN ATOM PROBE STUDY OF IRON CHROMIUM

The atom probe was used to study the microstructure of samples of Fe-Cr (32 at %) aged for different periods. The data were expected to reveal evidence of spinodal decomposition, with the wavelength of the sinusoidal fluctuations increasing with aging time. This paper discusses a statistical model for the data. A two-stage hierarchical model is used, in which the first stage models the spinodal decomposition, and the second stage models the sampling fluctuations introduced by the atom probe. Through estimating the parameters of the model, it is possible to smooth the data and obtain an estimate of the period of the sinusoidal fluctuations. This estimate can be used as a basis of comparison between different specimens. Devising statistical analyses that exploit information about the instrument and the alloy can yield more precise answers than exploratory methods based on the correlogram or the spectrum