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-ferrite or residual porosity, which can significantly impact the fatigue life of a part.
She looked up at Vega. “The alloy isn’t failing. It was never fully dense. The foundry skipped a degassing step. The voids were always there, but they were microscopic. Under stress, they coalesce. E562 found the truth.”
If the calculated %RA is too high, the statistical variation is too large. The operator must resolve this by analyzing more fields of view or using a grid with a higher density of test points. The standard provides mathematical tables and formulas to predict exactly how many fields are required based on a preliminary pilot run.
The test grid consists of a series of intersecting straight lines. The points of intersection form the test locations. Common grid configurations include symmetric square matrix arrays such as: ( 25-point grids ( 49-point grids ( 100-point grids ( The Boundary Counting Rules
A complete test report according to ASTM E562-19e1 should always include:
: Indicates the first editorial amendment to the 2019 edition, correcting non-technical metadata or typographic syntax without altering the core mechanical testing criteria.
) for each field. A minimum number of fields (often 10 to 30) must be evaluated to ensure statistical validity. 4. Statistical Accuracy and the %RA Metric
) represents the total volume of a specific phase divided by the total volume of the material. While we live in a three-dimensional world, measuring 3D volumes directly inside an opaque metal is destructive and incredibly difficult. ASTM E562 solves this by using —the science of interpreting 3D structures from 2D cross-sections. Stereological math proves that the point fraction ( Ppcap P sub p
For example, if you count 1000 total points across many fields, and 125 of them land on the phase of interest, that phase has a volume fraction of 12.5%. The standard also details how to calculate statistical outputs like the mean, standard deviation, and the ±95% confidence interval to quantify the uncertainty of the measurement.
is the globally recognized standard used by metallurgists and materials engineers to determine the volume fraction of an identifiable phase or constituent within a material’s microstructure using a systematic manual point count . Available through the ASTM International Store , this standard is essential in quality control, failure analysis, and material research. It allows engineers to quantify microstructures—such as the amount of pearlite in steel, porosity in additively manufactured metals, or the ferrite-to-austenite ratio in duplex stainless steels—with high statistical accuracy. The Core Principle: How Point Counting Works
The ASTM E562-19e1 standard is deployed across diverse metallurgy sectors:
. This is a critical preparatory step. The analyst visually estimates the area percentage of the target constituent. This estimation determines the appropriate grid size and the initial magnification.
A key feature of ASTM E562–19e1 is its proven reliability. A major study on cast Duplex Stainless Steel involved eight different laboratories measuring ferrite volume fraction on five different samples. The results demonstrated . Another study reported a precision under repeatability conditions of 5% .