A guide to using ASTM E562 Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count

The ASTM E562 Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count continues to be useful and important manual quantitative analysis method. It is applied in numerous industrial, military, and company specifications. For instance, AMS 2315 Determination of Delta Ferrite Content does not cite E562 but does describe a point count process that is nearly identical to it. ASTM E1181 cites its use for determining the volume fraction of each grain size in bimodal grain structures. Laboratories may find they must use ASTM E562 for any number of reasons. One is they simply do not have an automated image analysis system. Another is the microstructure does not lend itself to being segmented by an image analysis system even though the human eye can easily discern the constituent of interest. The image below shows a grain structure that would be very difficult to segment.

Figure 1. Customer Proprietary Nickel alloy etched with Lucas’ Reagent, 40X original magnification.

This presentation will walk through the procedure for systematic manual point count. It starts with visually estimating the area percentage of a constituent in order to select the appropriate grid size, and methods for superimposing the grid on the microstructure. Next the degree of statistical precision is chosen, which is the Percent Relative Accuracy (%RA), and from that the number of fields required to obtain the desired degree of precision is determined. Finally, the procedure involves creation of Excel work sheets for recording the individual field point count results and automatically calculating the % Volume Fraction, the Mean, standard deviation, ± 95% CI, and %RA.

Reference: ASTM E562-19 Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count