If too high, structure looks sparse; if too low, boundary decisions become impossible.
Low; requires perfect, uniform selective etching to prevent pixel misclassification.
By repeating this process over multiple randomly selected fields, the ratio of points falling on a phase to the total number of points provides an unbiased estimate of that phase's volume fraction.
A transparent grid composed of uniformly spaced points—formed by the intersection of horizontal and vertical lines—is superimposed on a microstructural image. This grid can be generated manually on a clear overlay or projected digitally through image-analysis software. Common grid formats include (16 points), (25 points), or (100 points). 2. The Counting Protocol
Understanding ASTM E562-19e1: The Standard for Manual Point Counting in Metallography astm e562-19e1
Calculate the standard deviation to determine the variability between fields:
P̄P=0.3125+0.21875+0.31253=0.28125 (or 28.13% Volume Fraction)cap P bar sub cap P equals the fraction with numerator 0.3125 plus 0.21875 plus 0.3125 and denominator 3 end-fraction equals 0.28125 (or 28.13 % Volume Fraction) Using the sample standard deviation formula, 95% Confidence Interval ( ): For fields (degrees of freedom ), the Student's -value at 95% confidence is 4.3034.303
ASTM E562-19e1 is the standard test method for determining the volume fraction of constituents in a material's microstructure using a systematic manual point count. The procedure, which is applied to metallographic sections, involves calculating volume fractions from point counts on a grid, often used to determine ferrite content in stainless steels. The full standard is available for purchase from ASTM International , ANSI, and other technical distributors. For the official text, visit ASTM International .
A standard metallurgical microscope (reflected light) or a monitor displaying a digital live feed from the microscope is utilized. 3. The Test Grid If too high, structure looks sparse; if too
Quantitative Description of the Microstructure of Duplex ... - MDPI
| Characteristic | ASTM E562-19e1 (Manual) | ASTM E1245 (Automated) | | :--- | :--- | :--- | | | Systematic manual point counting by a human operator. | Computer-controlled image segmentation and pixel counting. | | When to Use | * When an automated system is unavailable. * When the microstructure is complex and a computer cannot reliably distinguish phases. * For low-volume fractions or validation of automated results. | * For high-volume, repetitive analysis. * When the phases have clear, high-contrast boundaries. * When speed and throughput are the primary concerns. | | Relative Accuracy | Highly accurate and considered the reference method, but can be slow for large datasets. | Very fast, but accuracy is highly dependent on proper sample preparation and image thresholding. | | Context | Traditionally used for pore size distribution (PSD) analysis of nuclear fuels like U-Mo. | Automated methods using software like ImageJ and MATLAB are being validated as suitable alternatives to manual counting to improve efficiency. |
Measuring the amount of ferrite or austenite in duplex stainless steels.
The manual point count method involves placing a grid of points over a metallographic image (micrograph) of a polished and etched specimen. A technician then counts how many grid points fall within the specific phase of interest. Statistical Reliability in duplex stainless steels
For every chosen field of view, the operator evaluates each grid point (intersection):
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later.
Dual-phase (DP) and complex-phase steels require exact volume fractions of hard martensite islands embedded in a soft ferrite matrix to optimize crash energy absorption.
To fulfill the verification protocols demanded by ASTM E562-19e1, operators calculate the mean value and determine the standard deviation across multiple independent microscopic fields of view.
For example, in duplex stainless steels, a strict 50:50 balance of ferrite and austenite must be maintained to maximize pitting corrosion resistance and yield strength. If a manufacturing deviation yields an excess of ferrite, the material becomes brittle. Conversely, an overabundance of austenite diminishes its resistance to stress corrosion cracking.