An improved tint etcing method for high strength steel sheets with mixed microstructures.

Abstract

An improved tint etching method was developed to obtain a quantitative measure of the microstructure of high strength steel sheets with a mixed structure. The procedures of etching are presented with typical examples. The present method reveals ferrite in blue, martensite and retained austenite in light yellow, and bainite in brown. Each constituent is identified by electron microscopic observations of the same area on etched microstructure. The different colors are analyzed to be a result of difference in the thickness of etched films by means of Auger spectroscopy. The new method is com- bined with image analysis to determine quantitatively the fraction and morphology of microconstituent