In a lot of references commercially pure Titanium was included in difficult materials for metallography procedure. They have very low hardness and the inheritance of the material so in this particular application note some useful points gathered due to the future ease of metallography. It’s worth to mention that metallography of Titanium commercially pure family is a time-consuming procedure and require a lot of passion and effort. Above all, commercially pure titanium grade 1 have lower hardness than others so it makes it is metallography procedure double harder.
1. Procedures
In a point of view, the metallography procedure of commercially pure 1 titanium is divided into six steps namely sectioning, mounting, grinding, polishing, etching, and finally metallography as were demonstrated in Figure 1 graphically [1]. In this section, mentioned steps were described in detail for researchers, students, or who want to analyze the microstructure of the grade 1 commercially pure titanium.

Figure 1. Metallography workflow
1.1. Sectioning
In the first step, the specimen should be section into sub-size specimens due to ease of use in grinding, polishing, and metallography instruments. All metallography specimens were designed for sub-size specimens, so the upper boundary limitation is the workspace size of mentioned instruments.
The sectioning machine should select based on the precision and importance of the test. An Electric Discharge Wire Cut Machine (EDWM) with the consuming wire include in the best available options. Other methods like conventional wire cut or other laboratory methods are acceptable as far as they don’t introduce residual stress in the sub-size specimens. A smoother surface after sectioning makes the grinding step easier.
1.2. Mounting
Specimens are mounted in other materials not just due to ease of grinding and polishing but also ease of holding on the microscope and specimen collecting. There is two kind of mounting, cold and hot mounting. The method of mounting used in this study was hot mounting. Hot mounting could also be called hot biaxial pressing. It is a process in which a granulated polymeric material is softened, compressed, and cooled down sequentially. The process is carried out in a metallographic hot mounting press, designed for this application. Specimens after the mounting have shapes like Figure 2.

Figure 2. Specimens after mounting
1.3. Grinding
The grinding step isn’t an important step in the metallography of Titanium grade 1. But it is very important to choose one of the manual or automatic griding. In manual grinding, control on the specimen surfaces is very higher due to the slower pace of material removal. The author suggests using manual grinding because of the highly sensitive titanium. The schematic of manual grinding is shown in Figure 3. In manual grinding, the aimed surface of specimen grind in a rectangular shape SiC paper linearly. Usually, water is used for lubricating the contact surface. It is very important that the frontier direction of the specimen should change and rotate 90 degrees every 10 or 20 swaps of manual grinding avoiding wave formation on the surface of specimens.

Figure 3. Schematic of manual grinding
As in former work [2] explained, a 2000 SiC paper manual grinding with water lubrication were performed until the plain (it means all the scratches oriented in one particular direction).
For automatic grinding, a useful application note that Struers company released, named “Metallographic preparation of titanium” [2], mentioned grade 320 SiC paper with water lubrication until the plane surface with the 15 N/specimen force and 300 rpm can be applicable. The author is willing to mention that due to the low hardness of commercially pure Titanium, polishing with big particles like upper-micron diamond paste can fill the lack of proper grinding.
1.4. Polishing
Polishing of commercially pure titanium, in a specific way Titanium grade 1, is one of the most challenging preparations in metallography laboratories. One of the reasons is the low hardness of the Titanium and the other one is very strange small holes or scratches in the surface that appeared after polishing as demonstrated in Figure 4.

Figure 4. Scratches and holes that remain after polishing [2].
Aiming to eliminate any un-perfectionisms on the surface of as-polished titanium, a two-stage polishing is considered for commercially pure Titanium grade one. The primary stage is polishing with 1-micrometer diamond paste and the final polishing is performed with 0.05 µm Alumina suspension as shown in Table 1.
Polishing stage | Time | |
Primary | 1 µm diamond paste | 4-10 hours |
Final | 0.05 µm Alumina | 20-30 mins |
The primary step is performed with oil lubricant with 250 rpm circular velocity and a relatively high normal force on specimens. It’s worth mentioning that a polymer short-haired polishing pad was used. The specimen was rotated smoothly on its axis due to the homogenous polishing. The time of primary polishing is depending on the force of the hand, the density of diamond paste on the pad, and the situation of the specimen before the first stage of polishing. In four specimens that were polished successfully with this method, it took between 4 to 10 hours of polishing for each one.
The author suggests taking a picture from a specific part of the sample after a specific period to monitor the progress of eliminating scratches and holes in polishing. For instance, Table 2 monitor the upper section of welding Titanium grade 1 in the primary stage polishing procedure of it. The specimen was laser welded and sectioned with an electron discharge cutting machine.
Speed (rpm) | Time (min) | Photo |
150 | 0 | ![]() |
150 | 15 | |
150 | 30 | |
150 | 45 | Uniform and long scratches |
300 | 60 |
Another noticeable point is that the long and uniform scratches will be induced on the surface of the specimens and these uniform and long scratches will be eliminated in final polishing and they aren’t an important concern in primary polishing. Figure 5 demonstrated the specimen after the primary stage of polishing. It’s good to know that the surface of the specimen in this stage can be better than this condition that demonstrated but a long time of polishing results to skip this stage.

Figure 5. Specimen after primary polishing
The second stage of polishing is relatively shorter than the first stage. In the second stage, final polishing was performed with 0.05-micrometer alumina and a mixture of water and soap lubricant for 2 or 3 periods of 10 minutes. The final result of final polishing is demonstrated in Figure 6. As depicted, the final stage of polishing eliminates the sharp edge of small holes and removes the uniform and long scratches induced in the first stage of polishing.

Figure 6. Specimen after final polishing
The last but not least point of polishing commercially pure Titanium is that whenever the surface condition of specimens goes to the critical level that you want to reset the surface, don’t grind specimens again. Just polish it with the 1-micrometer diamond past and it refreshes the condition of the surface.
1.5. Etching
Etching of commercially pure grade 1 Titanium isn’t a time-consuming and hard step but it is a tricky one. A famous etchant for Titanium alloys is Kroll regent which consists of 2 ml HF + 6 ml HNO3+ 92 ml H2O. This reagent is very sensitive to the amount of time that elapses after mixing its components. The scale of it is in the level that a 5-10 second old regent can etch the Titanium grade 1 in 10 seconds of swapping but 10 minutes old of the same regent cannot etch the specimen for 2- or 3-minutes swapping at all. In an overview, the results are very dependent on the brand of regents and other parameters too. Figure 7 demonstrates a specimen that was well polished and etched with 10 seconds of swapping (2+3+5 seconds), but the Kroll regent was blended 1 or 2 minutes before swapping.

Figure 7. As etched X100 specimen 3, panorama
1.5. Metallography
Metallography is the name of the step in which mounted and etched specimens were taken under the microscope and the microstructure of them is observed.
Conclusion
Metallography of titanium grade 1 is one of the tricky and time-consuming metallographys between other metals. In the current study, a six-step method is investigated for the preparation of metallography samples and studying the microstructure of this specific metal.
References
[1] C. Fleißner-Rieger, T. Pogrielz, D. Obersteiner, T. Pfeifer, H. Clemens, and S. Mayer, “An additively manufactured titanium alloy in the focus of metallography,” Practical Metallography, vol. 58, no. 1, pp. 4-31, 2021.
[2] “Metallographic preparation of titanium.” [Online]. Available: https://www.struers.com/-/media/Struers-media-library/Materials/Application-reports/Application_Note_Titanium_2015_ENG.pdf