The new stereological tools in metallography: estimation of pore size and number in aluminium

Abstract

SUMMARY A number of simple, unbiased and efficient methods are now available in stereology for estimating the number and size of arbitrary particles or voids in a material, with the only assumption that particles must be identifiable on serial sections or confocal planes through the material. In recent years, these methods have been developed and applied mainly in a biomedical context: this paper reviews and illustrates them with the aid of a metallographic example, namely the pore population of a sand‐cast aluminium alloy. Our goal is to convey the fact that stereology is sampling in three dimensions, and therefore its principles remain valid and applicable in no matter what context. The disector, the selector, and an indirect method to estimate the distance between two parallel planes of polish are thereby illustrated. It is also shown how to split the error variance of the estimator of the pore volume fraction (‘porosity’) into the three components due to blocks, sections within blocks and systematic point counting on sections.