What are the methods of measuring grain size?

The grain size of specimens with two phases, or a phase and a constituent, can be measured using a combination of two methods, a measurement of the volume fraction of the phase and an intercept or planimetric count (see Section 17).

How do you calculate grains per square inch?

The expression for the ASTM grain size number n is written in terms of the number of grains per square inch at a magnification of 100x, as: N=2(n−1) N = 2 ( n − 1 ) .

How do I manually calculate grain size?

One of the simplest techniques to estimate an average grain size is the intercept technique. A random straight line is drawn though the micrograph. The number of grain boundaries intersecting the line are counted. The average grain size is found by dividing the number of intersections by the actual line length.

What is ASTM grain size?

 ASTM grain size number : the ASTM grain size number, G, is defined as : NAE = 2G-1 where NAE is the number of grains per square inch at 100X magnification.  Grain boundary intersection count : Determination of the number of times a test line cuts across, or is tangent to, grain boundaries.

What is the line intercept method?

The Line Intercept (LI) method is designed to sample within-plot variation and quantify changes in plant species cover and height over time using transects located within the macroplot. Transects have random starting points and are oriented perpendicular to the baseline.

Why are smaller grains stronger?

Smaller grains have greater ratios of surface area to volume, which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes.

How is the Heyn intercept method used to measure grain size?

To do the intercept method, one counts either grain boundary intersections, P, or grains intercepted, N, by the circles. For a single phase structure, it is easier to do P counts. For a two-phase structure, one must do N counts. For a single phase grain structure P = N and either count can be made.

How is the average grain size measured in MATLAB?

The MATLAB code for measurement of the volume-weighted average grain size is based on the point-sampled intercept length method defined by Gundersen and Jensen [25,26]. Similar to the ASTM E1382 procedure, intercepts are measured in four evenly spaced directions.

Are there any existing methods to measure grain size?

At present there are no established methods for the characterization of heterogeneous microstructures, and thus the suitability of existing methods is investigated. It is shown that existing methods can be applied when the measurement data is analyzed in a meaningful way.

When was the Heyn intercept method first used?

When ASTM standard E 2 was published in 1917, ASTM Committee E-4 on Metallography’s first standard, it described the planimetric method for measuring grain size based upon publications by Zay Jeffries, a founding member of E4; but, E 2 only briefly mentioned the intercept method developed in Germany in an appendix at the end of the standard.