1. Preparation of metallographic samples
To evaluate the microstructural changes after Aluminum Product Processing through metallographic analysis, the metallographic samples must be prepared first. This includes steps such as cutting, inlaying, grinding and polishing. When cutting aluminum products, care should be taken to avoid excessive heat-affected zones to prevent changes in the original microstructure of the material. Inlaying is to facilitate subsequent operations, especially for samples with irregular shapes. The grinding process should be carried out step by step from coarse sandpaper to fine sandpaper to remove surface damage caused by cutting and inlaying. When changing sandpaper at each step, it is necessary to ensure that the grinding direction of the sample surface is at a certain angle to the previous step, so that the scratches of the previous step can be better eliminated. Polishing is a key step. Use a suitable polishing agent, such as alumina suspension, to polish the sample on a polishing cloth until the surface is scratch-free and as bright as a mirror.
2. Observation under metallographic microscope
After preparing the metallographic sample, use a metallographic microscope for observation. When observing, first choose the appropriate magnification. For aluminum products, a low-power microscope (such as 50-100 times) can be used to observe macroscopic structural characteristics, such as the overall situation of grain size and distribution. High-power microscopes (such as 500-1000 times) are used to observe more subtle structures, such as phase distribution at grain boundaries, morphology and size of second-phase particles, etc. During the observation process, attention should be paid to the changes in microstructure in different areas. For example, in aluminum products that have been forged, grains may be seen to be elongated in areas with greater deformation, while in aluminum products that have been heat-treated, different phase structures may appear.
3. Analysis of microstructure characteristics
From the microstructure observed by the metallographic microscope, multiple characteristics can be analyzed to evaluate the changes after processing. Grain size is an important indicator, and the processing process often leads to grain refinement or growth. For example, during cold processing, the increase in dislocations caused by deformation will promote grain refinement, while unreasonable heat treatment may cause abnormal grain growth. Grain boundary characteristics are also critical. The distribution, morphology and number of second-phase particles at the grain boundaries will change due to the processing method. For example, in aluminum alloys, aging treatment will cause solute atoms to precipitate at the grain boundaries to form fine second-phase particles. The distribution and number of these particles will affect the strength and toughness of the material.
4. Comparison with standard and original organization
Finally, the observed microstructure should be compared with the standard organization map and the original organization of the aluminum product. The standard organization map can provide the microstructure characteristics that should be present after normal processing and treatment, helping to determine whether there are problems in the processing process. Comparison with the original organization can intuitively show the degree of change in the microstructure caused by processing, and then evaluate the impact of these changes on the performance of aluminum products. For example, hardness, strength, corrosion resistance and other properties may be closely related to changes in the microstructure. Metallographic analysis can provide a basis for optimizing the processing technology.
