Analysis of various metal structures under a metallographic microscope
For many years, metallographic workers have qualitatively described the microstructure characteristics of metal materials through microscope observation on the polished surface of metallographic samples, or evaluated microstructure, grain size, and non-metallic materials by comparing with various standard pictures. Mixtures and phase particles, etc., this kind of squareness is not high, and there is a lot of subjectivity in the evaluation, so the reproducibility of the results is not satisfactory, and they are all in the two-dimensional surface of the polished surface of the metallographic sample. When measured on a plane, there is a certain gap between the measured results and the real tissue description in three-dimensional space. The emergence of modern stereology provides people with a science of extrapolating from two-dimensional images to three-dimensional space, that is, the data measured on the two-dimensional plane and the theoretical microstructure shape, size, quantity and shape of the metal material in three-dimensional space. It is a science that connects the three-dimensional spatial structure, shape, size, quantity and distribution of materials with their mechanical functions, and provides reliable analytical data for scientifically evaluating materials.
Since the microstructure and non-metallic admixtures in metal materials are not uniformly distributed, the determination of any parameter cannot be determined by measuring one or several fields of view under a microscope with the human eye, and it is necessary to use accounting methods to determine sufficient Only by performing a lot of calculation tasks with more fields of view can the reliability of the measurement results be guaranteed. Assuming that only human eyes are used for visual assessment under the microscope, the accuracy, consistency and reproducibility are poor, and the determination speed is very slow, and some even cannot be carried out due to the heavy workload. The image analyzer replaces human eye observation and calculation with advanced electronic optics and electronic computer technology. It can flexibly and accurately carry out measurement and data processing with calculation significance. It also has high precision and good reproducibility, avoiding treatment The influence of factors on the metallographic evaluation results and other characteristics, and the operation is simple, and the measurement report can be directly printed, which has become an indispensable means in quantitative metallographic analysis at that time.
Microscope image analyzer is a powerful instrument for quantitative metallographic research on materials, and it is also a good helper for daily metallographic inspection, which can avoid subjective errors caused by manual evaluation, and then avoid the phenomenon of nonsense. Although it is impossible and unnecessary to use the image analyzer every time in the daily metallographic inspection, when the product quality is abnormal or the metallographic structure level is between qualified and unqualified and cannot be judged, the image analyzer can be used to analyze It conducts quantitative analysis to obtain accurate results and ensure product quality. The application of image analyzer in metallographic analysis has expanded the detection items of metallographic inspection, promoted the improvement of detection level, and is also very beneficial to improve the quality of detection personnel.
Introduction to the Principle and Function of Microscope Image Analyzer
The system of the image analyzer is an optical imaging system composed of a metallographic microscope and a microscopic camera stage, and its purpose is to make an image of a metallographic sample or photo. The metallographic microscope can directly carry out quantitative metallographic analysis on the metallographic sample; the microscopic camera table is suitable for analyzing metallographic photos, negative films and objects, etc.
In order to store, process and analyze images with computers, the images need to be digitized first. A frame of image is composed of a distribution of different gray levels, which is displayed as j=j(x, y) in mathematical symbols, where x and y are the coordinates of pixels on the image, and j indicates its gray value. Therefore, a frame of image can be displayed with an m×n-order moment leakage, each element in the moment corresponds to a pixel in the image, and the value of aij is the grayscale of the pixel belonging to the i-th row and j-th column in the leakage display image value. A CCD camera (Charge Coupled Device Camera) is an image digitization device. The microscopic features on the metallographic sample are imaged on the CCD after passing through the optical system, and the photoelectric conversion and scanning are completed by the CCD, and then taken out as an image signal signal, expanded by the expander, quantified into gray levels, and stored , and then get the digital image. The computer sets the gray value threshold T according to the gray value limit of the feature to be measured in the digital image. Regarding any pixel in a digital image, if its grayscale is greater than or equal to T, then replace its original grayscale with white (grayscale value 255); if it is less than T, replace its original grayscale with black (grayscale value 0). The grayscale can convert the grayscale image into a binary image that only needs two grayscales, black and white, and then perform the required processing on the image, so that the computer can conveniently perform particle counting, area, and perimeter on the binary image. Image analysis obligations such as measurement. If pseudo-color processing is used, 256 gray levels can be converted into corresponding colors, so that details with close gray levels and their surrounding conditions or other details are easy to identify, thereby improving the image and making it easier for computers to process multi-feature images .
