Analysis of Various Metal Microstructures Under a Microscope
For many years, metallographic practitioners have qualitatively characterized the microstructural features of metallic materials by observing the polished surfaces of metallographic specimens under a microscope. They also evaluate microstructure, grain size, non-metallic inclusions and phase particles through comparison with various standard images. This method has low accuracy and strong subjectivity during evaluation, resulting in unsatisfactory repeatability of test results. In addition, all measurements are conducted on the two-dimensional polished plane of metallographic specimens, so the measured data differ noticeably from the real three-dimensional microstructure of materials.
The emergence of modern stereology provides a scientific method to extrapolate three-dimensional structures from two-dimensional images. It correlates the data measured on a 2D plane with the theoretical morphology, size, quantity and distribution of the three-dimensional microstructure of metallic materials. Furthermore, it establishes an intrinsic correlation between the 3D structural characteristics and mechanical properties of materials, providing reliable analytical data for the scientific evaluation of materials.
Since the microstructures and non-metallic inclusions in metallic materials are unevenly distributed, the determination of any parameter cannot rely merely on human visual observation of one or several microscopic fields of view. Statistical calculations on a sufficient number of fields are required to ensure the reliability of measurement results. Manual visual assessment under a microscope suffers from poor accuracy, consistency and repeatability, along with extremely low testing efficiency. In some cases, the workload is too heavy to complete the evaluation manually.
Image analyzers replace human observation and manual calculation with advanced electron optics and computer technology. They can rapidly and accurately perform statistically significant measurements and data processing. Featuring high precision and excellent repeatability, they eliminate human interference in metallographic evaluation. With simple operation and direct printing of test reports, image analyzers have become an indispensable tool in quantitative metallographic analysis.
The microscopic image analyzer is a powerful instrument for quantitative metallographic research and daily routine metallographic inspection. It eliminates subjective errors caused by manual assessment and avoids disputes arising from inconsistent judgment. Although it is unnecessary to use an image analyzer for every routine inspection, it can be adopted for quantitative analysis when product quality anomalies occur or when the metallographic grade lies on the borderline between qualification and disqualification. It delivers accurate results to guarantee product quality. The application of image analyzers expands the inspection items of metallographic testing, improves the overall testing level, and greatly helps enhance the professional competence of inspection personnel.
