The choice of a metal alloy for a particular purpose cannot always be made on the basis of previous data. The properties of the material may change during processing in such a way as to affect, sometimes irreversibly, the properties required in service. It follows that the control of construction materials, whether ferrous or non-ferrous, is now an indispensable phase within the production cycle and affects various product areas. Optical metallography, an extremely versatile and rapidly applicable technique, allows the characterization of the test specimen from a structural point of view, providing immediately a great deal of information both on the raw material supplied and on the finished product, which may have undergone heat treatment. Together with hardness measurement and chemical analysis, the method provides a valid tool for the physical characterization of the material under investigation.
The microstructure is highlighted in the material by chemical etching of the appropriately polished surface on supports of defined grain size. The APM metallography laboratory has about 200 different etching solutions, which are used depending on the type of material to be examined and the features to be highlighted.