Analysis of Various Metallographic Structures under the Microscope
For many years, metallographers have qualitatively characterized the microstructure features of metallic materials by microscopic observation on the polished surfaces of metallographic specimens, or evaluated microstructure, grain size, non-metallic inclusions, second-phase particles and so on by comparison with various standard micrographs. This method has low accuracy and strong subjectivity during evaluation, and the repeatability of results is unsatisfactory. All measurements are performed on the two-dimensional plane of the polished metallographic specimen surface, so there is a certain deviation between the measured results and the real three-dimensional microstructure. The emergence of modern stereology provides a scientific method to extrapolate three-dimensional information from two-dimensional images. It correlates data measured on 2D planes with the theoretical morphology, size, quantity and distribution of microstructures of metallic materials in 3D space. It can establish the inherent relationship between the 3D microstructure morphology, size, quantity, distribution and mechanical properties of materials, providing reliable analytical data for material evaluation.
Since microstructures and non-metallic inclusions in metallic materials are not uniformly distributed, measurement of any parameter cannot be determined merely by observing one or a few fields of view with the naked eye under a microscope. Statistical analysis of a sufficient number of fields of view is required to guarantee the reliability of measurement results. Visual assessment only by human eyes under the microscope suffers poor accuracy, consistency and repeatability, together with low measuring speed; some tests are even impossible to carry out due to excessive workload. Image analyzers adopt advanced electron-optics and computer technology to replace manual visual observation and statistical calculation. They can rapidly and accurately perform statistically meaningful measurements and data processing. Featuring high precision and good repeatability, they eliminate the influence of human factors on metallographic evaluation results. Easy to operate, they can directly print measurement reports and have become an indispensable tool for quantitative metallographic analysis.
