Metallographs and graphs (also short for technical assistant for metallography and physical material analysis or TA for metallography and material analysis , formerly abbreviated as MET ) are technical specialists who dedicate themselves to metallography . The focus here is on the preparation of metallographic (or "materialographic", if one does not want to limit oneself to the metals) sections, thin sections and cuts as well as further structural analysis. As a rule, this is done with the methods of light microscopy (LM), scanning electron microscopy (SEM), scanning probe microscopy (AFM, STM), X-ray structure analysis , spectroscopy and radiographic testing .
The preparation for classic surface analyzes includes the production of a mirror-like, ideally absolutely flat surface, which is then contrasted by means of etching. The structure becomes visible and assessable. The structural assessment naturally includes knowledge of the constitution, as this is the only way to make a meaningful assessment of the phases present in the material. From the crystal structure of mostly metals made visible in this way, far-reaching conclusions can be drawn about the material components, production, processing, heat treatment and loading. In the event of damage, metallographic examinations can usually determine the reason for the failure of a material.
The preparation of workpieces for examination alone requires extensive material knowledge and a lot of practice, since the flat surfaces have to be ground and polished by hand to the nearest micrometer, completely scratch-free. The mechanical production of polished sections is only possible if known and standardized test pieces can be processed, because a corresponding number of test pieces is required to set up the corresponding machines. In the event of damage in particular, however, there is only one test piece to be examined, which is then only manufactured by hand with the necessary precision and prepared for examination, i.e. H. can be ground and polished. The metallographer acquires these skills as part of his training.
The range of tasks of the metallopgraph also includes hardness tests , determination of tensile strength and the determination of other mechanical properties. In addition to purely scientific work, the metallograph forms the link between development and production on the one hand and damage assessment on the other.
In the past, the field of duties of the metallographer has been steadily expanded, so that now, in addition to the classic structural assessment, damage analysis and many other analysis methods are also part of his resort. In the course of the last century, the range of assessment and tasks performed by metallographers was expanded to include plastics, ceramics and other materials. In addition to the pure analysis and consideration, he also has an advisory role for designers and engineers in order to point out problematic constellations at an early stage.
The constant advances in technology also lead to an ongoing change in the skills required of a metallographer. Since microscopic and other examinations are documented photographically, it was necessary before digitization that the metallographer also received extensive training in photography and photochemistry. Most of the photographic documentation was carried out on 6 * 9 or 9 * 12 negative film until digitization. The use and processing of such materials required extensive knowledge. The digitization led to a shift away from classic photo chemistry towards digital image processing.