Three dimensional morphology of cementite precipitates

Abstract

Conventional light and electron microscopy techniques usually allow for characterization of microstructures in only two dimensions. This is a serious impediment to understanding the three dimensional morphology of microstructural features. This paper presents the results of a deep etching study of cementite precipitates in a model alloy composed of Fe-1.34 wt.% C-13.1 wt.% Mn. The high carbon level enables a large volume fraction of cementite precipitates to be produced while the high manganese and carbon levels together suppress the martensite start temperature to below room temperature. During deep etching of this alloy, the austenitic matrix is preferentially removed and the morphology of the cementite precipitates is revealed. This also enables complimentary crystallographic and interfacial structure studies which are underway. Although previous investigations used deep etching as a supplementary technique for characterizing cementite plates, the current work places emphasis on determining the three dimensional morphology of both grain boundary and intragranular precipitates previously categorized under the two dimensional Dube morphological classification system.