Introducción a la aplicación campo de metalográfico microscopio
Metalográfico examen de ferrosos metales, metalográfico examen de no ferrosos metales, metalográfico examen de polvo metalurgia, tejido identificación y evaluación después material superficie tratamiento.
Check: raw material check and process check.
Muestreo inspección: El producto fabricación proceso conducta metalográfica inspección en semiacabado productos para asegurar que la microestructura de el producto cumple el procesamiento requisitos de el siguiente proceso.
Proceso evaluación: Juzgar y identificar la cualificación de producto proceso.
En servicio evaluación: Proporcionar a base para el rendimiento, confiabilidad y servicio vida de en-servicio piezas.
Fallo análisis: encontrar proceso y material defectos, so as a proporcionar macro y micro análisis base para fallo análisis.
Varios imagen principios de metalográfico microscopio
1. Brillante campo, oscuro campo
Bright field is the most basic way to observe samples with a microscope, and it presents a bright background in the field of view of the microscope. The basic principle is that when the light source is irradiated vertically or nearly vertically through the objective lens to the sample surface, it is reflected back to the objective lens by the sample surface to make an image.
The difference between the dark field illumination method and the bright field is that there is a dark background in the microscope field area, and the illumination method of the bright field is vertical or vertical incidence, while the illumination method of the dark field is through oblique illumination around the objective lens. La muestra, la muestra será dispersa o refleja la irradiada luz, y la luz dispersa o reflejada por la muestra entra el objetivo lente a imagen la muestra. Oscuro campo observación puede claramente observar incoloro y pequeño cristales o claro-coloreado fino fibras que son difíciles observar en campo brillante en oscuro campo.
2. Polarizado luz, interferencia
The polarization of light can be detected with the aid of experimental setups. Take two identical polarizers A and B, let the natural light pass through the first polarizer A first, then the natural light also bevenes polarized light, but the second polarizer B is needed because the human eye can distinguish it. Arreglar el polarizador A , lugar el polarizador B en el mismo nivel como A , girar el polarizador B , y usted puede encontrar eso la intensidad de la transmisión luz cambios periódicos con la rotación B % 2c y la luz intensidad voluntad gradualmente cambiar desde máximo máximo cada 90 grado rotación. Debilitar a el más oscuro, y luego girar 90 grado , la luz intensidad voluntad gradualmente aumentar desde el más oscuro a el más brillante , así el polarizador A es llamado un analizador.
Interference is a phenomenon in which two columns of coherent waves (light) are superimposed in the interaction area to increase or decrease the light intensity. The interference of light is mainly divided into double-slit interference and thin-film interference. Double-slit interference means that the light emitted by two independent light sources is not coherent light. The double-slit interference device makes one beam of light pass through the double slit and become two beams of coherent light, which communicate on the light screen to form stable interference fringes. In the double-slit interference experiment, when the path difference from a point on the light screen to the double slit is an even multiple of the half-wavelength, bright fringes appear at the point; when the path difference from a point on the light screen to the double slit is an odd multiple of the half-wavelength , the dark fringe at this point is Young's double-slit interference. Thin-film interference is the phenomenon of interference between two beams of reflected light after a beam of light is reflected by the two surfaces of the film, which is called thin-film interference. In thin-film interference, the path difference of reflected light from the front and rear surfaces is determined by the thickness of the film, so the same bright fringe (dark fringe) should appear at the place where the thickness of the film is equal in thin-film interference. Since the wavelength of light is extremely short, when thin films interfere, the dielectric film should be thin enough to observe interference fringes.
3. Differential interference contrast DIC
Metallographic microscope DIC uses the principle of polarized light. Transmission DIC microscope mainly has four special optical components: polarizer, DIC prism I, DIC prism II and analyzer. Polarizers are installed directly in front of the condenser system to linearly polarize the light. A DIC prism is installed in the condenser, and this prism can decompose a beam of light into two beams of light (x and y) with different polarization directions, which form a small angle. The condenser aligns the two beams of light parallel to the microscope optical axis. Initially, the two beams of light have the same phase. After passing through the adjacent area of the specimen, due to the difference in the thickness and refractive index of the specimen, the two beams of light have an optical path difference. A DIC prism II is installed at the back focal plane of the objective lens, which combines the two light waves into one. At this time, the polarization planes (x and y) of the two beams of light still exist. The last beam passes through the first polarizing device, the analyzer. Before the beam forms the eyepiece DIC image, the analyzer is at right angles to the direction of the polarizer. The analyzer combines two perpendicular beams of light into two beams with the same plane of polarization, causing them to interfere. The optical path difference between the x and y waves determines how much light is transmitted. When the optical path difference is 0, no light passes through the analyzer; when the optical path difference is equal to half the wavelength, the light passing through reaches the maximum value. Therefore, on the gray background, the structure of the specimen presents a difference between light and dark. In order to achieve the best image contrast, the optical path difference can be changed by adjusting the longitudinal fine-tuning of the DIC prism II, which can change the brightness of the image. Adjusting the DIC prism II can make the fine structure of the specimen present a positive or negative projection image, usually one side is bright and the other side is dark, which causes the artificial three-dimensional sense of the specimen.
