Determination of average grain size

What is it?

The formation of the grain in metals and metal alloys occurs when these materials are activated thermally (by melting or heat treatment for example), and thus subject to atomic scale rearrangements. Also, mechanical processes of deformation can interact with the size and shape of the grain. These processes lead to the formation of different microstructures, where one of the interesting characteristics to know is the average size of the grains that make up the microstructure.
Grain size is a parameter of quantitative metallography that evaluates the average grain size that constitutes the material. There are several possibilities for this quantification, such as counting the number of grains in a given area or reference length, and comparing with reference letters. For this analysis the samples are prepared according to the procedures of the preparation of samples for metallography, and analyzed under microscopy.

What is it used for?

The study of metallography, in this case average grain size, allows the observation of the microstructure of metals and metal alloys, which can be related to the physical/chemical properties and their mechanical behavior.

Equipment and working conditions

The equipment used to perform the evaluation of the average grain size are:
- Nikon optical microscope, Optiphot model with 50X, 100X, 200X, 400X and 1000X magnification;
- ZEISS optical microscope, Imager.Z2m model with 50X, 100X, 200X, 500X and 1000X magnification.

Example of use

Study of the mechanical behavior of materials
Susceptibility of failure occurrence due to mechanical rupture
Correlation with the ability to obtain high degree of finish in polished parts