On the sampling methodology to characterize microsegregation

The heterogeneities formed during the solidification – the so-called microsegregation – play an important role in understanding the solidification behavior of an alloy. Their experimental characterization requires chemical analysis at the scale of a micron, usually EPMA or EDS analysis, over surfaces of hundreds of square microns. The resulting number of measurements for a single analysis is therefore important. Some efforts have been made to set-up a method to improve the reliability of the chemical analysis with the minimum required measurements. Despite the advances in this field, no clear rules were established. Using descriptive statistic tools, the present paper compares the results obtained with two different sampling strategies for characterizing microsegregation in a TiAl-based alloy. The author introduces a scaling factor f that accounts for the characteristic microstructure lengths, and is shown to be an important parameter in order to improve the estimate of the segregation parameters. Based on these results, an alternative methodology is proposed.