Specimens of metallic alloys, i.e., to be studied with EBSD (electron backscatter diffraction), should be mounted so that they are in a stable medium. Hot mounting is a protective measure, as well as one which eases handling of the specimen and permits multiple specimens in one mount.
How is the specimen prepared?
Cleaning is an essential preliminary step to the hot mounting process. Acetone should be used, and an ultrasonic bath may be needed. Any handling of the specimen should occur with gloves on. The ideal hot mounting resin must also be selected.
Hot mounting resins have low-shrinkage and are acid-resistant, hard materials. For example, Epoxy resin is a black thermosetting resin that has excellent edge retention. Acrylic resin, on the other hand, is clear and allows for easy observation.
How does hot mounting occur?
The cleaned specimen is positioned in the hot mounting press, within a mounting cylinder, along with the mounting resin. A high temperature is activated (around 180 degrees Celsius) in relation to the embedding process. Pressure is also be applied in the process.
There are two kinds of hot mounting resin: thermosetting and thermoplastic. Thermoplastic resins can be melted again and remoulded after an initial press. With thermosetting resins, a specimen can only be removed from a cured mount if it is destroyed. In the process of hot mounting, the pressure must remain constant with thermosetting resins; it is otherwise possible to produce non-uniform mounts.
Certain specimens may be temperature sensitive, in which case the temperature can be lowered to around 150 degrees Celsius.
What problems may occur?
There are various issues that may arise during the hot mounting process, such as blistering, which may be a consequence of the heating time not being long enough or gas being trapped within the mount. It is generally easy to find solutions.
