Experimental technique for observation of three-dimensional metallography in brass and carbon steel

In the present study, an experimental technique is proposed by which the three-dimensional (3D) metallography (or crystals) can be observed on a fracture surface. The observation of the 3D metallography in brass and carbon steel has enabled their microstructural characteristics to be clarified. In brass, unique 3D lead crystal shapes were detected on the fracture surface with 'butterfly' and 'grass-like' shapes. On the other hand, grain boundaries and laminar shaped cementite were revealed in 3D for medium carbon steel. To obtain such 3D metallography, the samples were cooled to -196°C during the fracture process, produced by a compressive load. The essence of this approach was to embrittle the material, especially grain and crystal boundaries, during the fracture process. This helped to reveal the true shape of a variety of phases. Details of the mechanism for revealing the 3D metallography are discussed.