The metallography’s roots trace back to the 18th century due to the rise of industrial technology and the growing need for metal. The mechanical properties of a material are heavily dependent on the microstructure of the material. Porosity, inclusion, second phases, and grain size play a central role in the material’s quality, strength, and durability (Boileau, 2020). There are various methods to determine many of these factors: for porosity, it relies on the number of grid intersections in relation to the number of grid lines. While porosity, inclusion, and second phases cannot be altered after the material was solidified, other factors such as grain size can be changed through various processing forms. Doing so can drastically improve the quality of the material; thus, there exist many ways of analyzing and altering the grain size.
Grain size determination methodology relies on the use of reference plates to measure distances on photographs taken of the polished and etched microstructures. Two standard methods are “Lineart Intercept” and “Circular Intercept,” with the first analysis relying on the number of points where the drawn line intersects a grain boundary. The second method relies on measuring intersections between circular grain boundaries. Using these two methods, it becomes possible to determine the quality and properties of the material. While manual measurement methods are overall reliable, the automated methods are far more commonly used, despite their pricing. It uses digital photography and software to capture images and then process them to analyze features that otherwise would be difficult to determine. While there are free-to-use software programs for automated measurement, it requires a professionally trained person to do so. Therefore automated methods become more expensive with needed time and resources to hire or train a professional metallographer and obtain the necessary applications and technology.
Reference
Boileau J.M. (2020). Metallography. BE 1310 Laboratory.