Metallography plays an important role in the quality control of titanium and its alloys, from initial production process monitoring, to casting porosity assessment and heat treatment control. It also plays an important role in the development of titanium alloys and products.
At 882°C, titanium undergoes an isotropic transformation from a close-packed hexagonal structure (α) at low temperatures to a body-centered cubic structure (β). This transformation can be used to produce α-type, β-type, or mixed α-β-type microstructure alloys and can be used for heat treatment and thermo-mechanical treatment.
As a result, a wide variety of properties can be obtained with relatively few alloy components. However, in order to ensure the ideal combination of microstructure and properties, tight control of the treatment process must be maintained. This makes metallography very important. In the production of titanium and titanium alloys, the relationship between hot forming, heat treatment, microstructure and physical properties is very complex. Examples of the most common microstructures of titanium are shown below. Because of its high toughness, titanium often produces long chips when processed or cut. Therefore, the use of conventional alumina cutting wheel for metallographic cutting is not effective and often leads to thermal damage. Cutting titanium produces a specific odor that is very noticeable when cutting large or large amounts of titanium. In primary production control laboratories, which mainly analyze titanium ingot, billet and plate, large titanium samples are usually not inlaid when processed. However, smaller manufactured components, such as wires and fasteners, should always be inlaid. This simplifies sample preparation and ensures optimal accuracy and reproducibility of results.
Preparation of titanium and titanium alloys: Grinding and polishing. Due to its high toughness, titanium is prone to mechanical deformation and scratches in the process of metallographic preparation. Diamond polishing should be avoided, especially for commercial pure titanium, as it can cause mechanical deformation in the form of scratches and oil stains on the surface. Once formed, this layer of deformation is difficult to remove. To avoid this problem, we recommend chemical mechanical polishing. Mixtures of nitric acid and hydrofluoric acid can also be used for chemical-mechanical polishing of titanium. These reagents work very quickly. However, we do not recommend using them for polishing because they are highly corrosive and good safety measures must be taken when using these acids in the polishing process.
