This document discusses three standard ASTM methods for measuring grain size: the comparison method, planimetric/Jeffries' method, and intercept method. The comparison method involves comparing a grain structure to graded images or overlays at 10x magnification, with a repeatability of ±1 grain size number. The planimetric method counts grains within a known area at higher magnifications from 100-500x, achieving ±0.25 grain size units precision. The intercept method counts the number of grains intercepted by a test line, allowing measurement of elongated grains faster than the planimetric method at the same precision of ±0.5 grain size units.

1. Grain Size Measurement
According To ASTM
Standards
Jabin Mathew Benjamin
13MY04
Dept. of Metallurgical Engineering

2.  ASTM standard E112-10
 Determination of planar grain size
 A microscopically-determined grain size of No. 1
has 1.000 grains/in2 at 100X

3. GRAIN SIZE
MEASUREMENT
Comparison
procedure
Planimetric
procedure
Intercept
procedure

4.  Comparison Procedure
◦ Comparison of the grain structure to a series of
graded images
 Wall chart
 Clear plastic overlays
 An eyepiece reticle.
Use with a 10X objective
The following chart was used to make this image
METHODS FOR DETERMINING
THE AVERAGE GRAIN SIZE
ASTM METHODS E 112
PCN 12-501 120-10
Plate 1B
Untwinned Grains
100X

5. ◦ Repeatability and reproducibility of ±1 grain
size number.
◦ Specimens consisting of equiaxed grains.
 Comparison Charts
◦ Plate I—Untwinned grains (flat etch).
◦ Plate II—Twinned grains (flat etch)
◦ Plate III—Twinned grains (contrast etch)
◦ Plate IV—Austenite grains in steel

6.  Planimetric or Jeffries’ Procedure
◦ Involves an actual count of the number of grains within a
known area.
◦ Number of grains per unit area, NA, is used to determine
the ASTM grain size number, G.
◦ Repeatability and reproducibility of ±0.25 grain size units
◦ Require marking off of the grains as they are counted.

7. Relationship Between Magnification Used and Jeffries’
Multiplier, f, for an Area of 5000 mm2 (f= 0.0002 M2)

8.  Intercept Procedure
◦ Actual count of the number of
 grains intercepted
 grain boundary, per unit length of test line
◦ Lineal intercept length, used to determine the ASTM
grain size number, G.
◦ Repeatability and reproducibility are less than ± 0.5
grain size units.
◦ Faster than the planimetric method for the same level of
precision.
◦ Structures consisting of elongated grains.

9.  Heyn Lineal Intercept Procedure
◦ The number of grains intercepted by one or
more straight lines sufficiently long to yield at
least 50 intercepts.
◦ Intercept
◦ Intersection
 Circular Intercept Method
◦ Automatically compensate for departures from
equiaxed grain shapes
◦ Ambiguous intersections at ends of test lines
are eliminated

10. ASTM No. 0 has a mean intercept
size of 32.00 at 100X.
 lo = 32.00mm

11. Reference
 Abrams, H., “Grain Size Measurement by
the Intercept Method,” Metallography , Vol
4, 1971, pp. 59–78.
 “Methods for determining the average
grain size” ASTM methods E 112 PCN 12-
501 120-10

12. THANK YOU