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Metallographic analysis: from concept to key technologies and equipment
2026-04-30
What is metallography?
Metallography, the study of the internal structure of metals and alloys, focuses not only on the microstructure of materials in a static state but also on the impact of external conditions or internal factors on the internal structure.
Metallographic structure refers to the microscopic morphology within metals. Common structures include martensite, austenite, ferrite, pearlite, etc. The morphology, size, and distribution of these structures directly determine the macroscopic properties of metal materials.
Core sample preparation process and equipment
Standard sample preparation process: cutting → mounting → grinding and polishing → etching → observation.
The first three links are particularly crucial, involving the following core equipment and consumables.
1. Cutting - Obtaining Test Samples
The metallographic cutting machine is the first step equipment for sample preparation, helping us cut samples of suitable size from large pieces of material.
Core function: Equipped with a high-speed rotating cutting blade, it can efficiently cut materials such as metal and rock.
Key technology: Built-in cooling system, which sprays cooling liquid to remove heat during cutting, effectively preventing tissue burns caused by overheating of the specimen.
2. Inlaying - Protection and fixation
The metallographic mounting press is used for mounting small, irregularly shaped, or specimens requiring edge protection, facilitating subsequent grinding and polishing.
Core function: The specimen is encapsulated in resin material through hot pressing or cold curing to form a cylindrical body of uniform specifications.
Supporting consumables: Choose different colors of mounting materials according to your needs - black or transparent for routine observation, and conductive mounting materials for electron microscopy analysis.
3. Grinding and polishing - obtaining a mirror finish
The metallographic grinding and polishing machine is used to complete the two processes of grinding and polishing, treating the sample surface to achieve a mirror-like shine. This process involves the coordinated use of various consumables.
(1) Metallographic sandpaper
Using silicon carbide abrasives and electrostatic sand planting technology, the particles are uniform and the cutting is sharp. The water-resistant design prevents clogging when used with water flow. Grinding is performed step by step from P80 to P4000 mesh size to obtain a flat surface.
(2) Polishing agent and polishing fabric
Metallographic polishing agent: Disperse fine abrasive particles in a medium, with particle sizes ranging from W20 to W0.5. The smaller the number, the higher the precision.
Metallographic polishing fabric: used to carry polishing agents. Depending on the hardness of the specimen and the requirements for rough/fine polishing, polishing cloths with different pile lengths (velvet, flocked, etc.) are selected.
Metallographic structure analysis
After completing the sample preparation processes such as cutting, mounting, grinding, and polishing, a mirror-like bright surface of the sample is obtained. Now, we can proceed to the core step of metallographic analysis: etching and observation.
1. Corrosion - Unveiling the Structure
After polishing, the mirror-like sample can only reveal a flat surface with blurred grain boundaries under a microscope. This is because different microstructures have similar reflective abilities towards light, making it difficult to distinguish between them. Therefore, chemical or electrolytic etching is required to make the differences between different microstructures visible.
2. Observation - Interpreting the Microscopic World
The metallographic microscope is a core equipment for observation, used to observe and record the microstructure of specimens, and serves as a bridge connecting sample preparation and result interpretation.
Mastering metallographic analysis technology requires not only familiarity with equipment and consumables, but also an understanding of the principles behind each step of operation. Because the quality of the final analysis is entirely dependent on the precision of sample preparation.
