Metallurgical microscopy is used for metallographic analysis. Generally speaking, there are several types.
1. Upright metallurgical microscope - easy to select the field of view (sample preparation should be flat on both sides).
2. Inverted metallurgical microscope - convenient, the bottom of the sample is not demanding.
3. Stereo microscope - fracture and macroscopic inspection.
4. On-site metallurgical microscope - used to measure large samples that cannot be made.
The visual function of metallurgical microscope is divided into: brightfield, darkfield, polarized light, differential interference dic and other observation methods.
Let's take a look at the uses of a few ways to observe:
Brightfield: Illumination light is used to directly irradiate the surface of the sample to be measured and reflected back for observation. The most commonly used observation method, the surface of the sample is slightly uneven and no shadow, which can show a variety of different tissue morphologies more realistically. Field is a function of all metallographic microscopes, and conventional metallographic is generally observed in brightfield.
Darkfield: Using the diffraction diffraction of light generated by the Tindal phenomenon, the test sample can be observed by oblique illumination, and the material that cannot be seen in the brightfield can be seen. Non-metallic inclusions can be identified.
Polarization: Taking advantage of the unidirectional vibration of polarized lenses, it is possible to qualitatively inspect substances with birefringence when vertically orthogonal. It is suitable for the identification of geological lithofacies and crystalline inclusions. Differentiation of isotropic crystals from anisotropic phases; distinguish isotropic phases with different degrees of corrosion; According to the different rotation angles of the vibrating surface of grains with different orientations, the degree of brightness and darkness is different, and the fine structure such as twins and grain boundaries is distinguished. Inclusion inspection.
Differential Interference Contrast Microscope (DIC): In 1952, Nomarski invented the differential interference contrast microscope on the basis of the principle of phase contrast microscope, which uses the interference phenomenon of linear polarized light after passing through the Nomarsky prism to observe the concave and convex surface of the sample, which has the advantage of a stronger three-dimensional sense of the image, which greatly improves the observation of some tissues. Such as carbides precipitated on grain boundaries.
Darkfield Observation DIC Observation