Transmission electron microscopy of deep etched cementite

A novel transmission electron microscopy (TEM) sample preparation technique was applied during a study of proeutectoid cementite precipitates in a Fe–1.34 wt.% C–13.0 wt.% Mn alloy. In isothermally transformed specimens, the material contains interconnected networks of grain boundary and Widmanstätten cementite precipitates. By immersing conventionally prepared (dimpled and electropolished) TEM specimens in an etching solution, the three-dimensional morphology and internal structure of entire electron transparent cementite precipitate networks were revealed to provide insights that were not previously possible. This paper describes the experimental technique and illustrates the benefits of this technique by comparing present results with observations of thin foil specimens of the same alloy.