Quantification of Rapidly Solidified Microstructure of Al-Fe Droplets Using Correlation Length Analysis

A novel characterization technique for quantifying solute segregation and primary phase formation in rapidly solidified spray-atomized powders is presented. The method uses the two-point correlation function to analyze solute concentration maps obtained by X-ray tomography analysis. The two-point correlation function analysis enables a statistical characterization of the scale of structure in solidified powders, yielding information about the in-plane primary phase size, spacing, and anisotropy as a function of depth through the sample. The technique is used to study the microstructure of Al-Fe powders solidified at different cooling rates. The change in spacing as a function of cooling conditions and depth through several samples is characterized.