ASTM E() – Standard Test Methods for Determining Average Grain Size Using Semiautomati. Purchase your copy of ASTM E – 97() as a PDF download or hard copy directly from the official BSI Shop. All BSI British Standards. The ASTM Designation: E–97 requires five hundred data points for a given sample and this analysis is time-consuming and tedious for the.
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The boundaries are reasonably well developed and the specimen can be analyzed with a digitizing tablet but some editing would be required for automatic image analysis.
The number of intersections of the grain boundaries by the scan lines is determined. Measure areas of whole grains only. In this case, the average number of intercepts or intersections should be at least 25 per circle. Reference 1 provides guidance for development of prior-austenite grain boundaries.
Delete all grains intersecting the test area border from the image so that partial chord lengths within these grains are not measured. Using the equation relating either P and G or? Such a computation is easy to perform e1832 the data can be read into a spreadsheet type computer program. For each of the three principle test planes, three directions perpendicular to those shown in Fig.
The presence of twin boundaries can be tolerated when semiautomatic digitizing tablets are utilized but measurement errors are more likely to occur. If the anisotropy index, or other descriptions of the grain e132, was determined see Annex A1report the value s for the plane or planes, or directions evaluated.
However, the presence of an equiaxed grain structure in a wrought specimen can only be determined by examination of a plane of polish parallel to the deformation axis. L P mm-1 For measuring intercept lengths, a test grid with a number of equally spaced straight, parallel lines is used.
For such structures, use the lowest possible magni? Permission rights to photocopy the standard may also be secured from the ASTM website www. Determine the average enlargement factor of the measured features and multiply this value by the magni?
There are a number of missing grain boundaries that must be added before measurement. This ideal range may not always be achievable depending upon the available magni? Because of the need to mark off the grains as they are counted, this method is best utilized with photomicrographs.
For accurate measurement of grain intercept chord lengths or grain areas, the smallest grains should be at least 5-mm in diameter on the television monitor see In general, coarse-grained specimens are more easily etched for prior-austenite grain size.
The simplest is to? Subjecting the specimen to a temper embrittlement cycle may enhance the etch response, but this treatment is not helpful if the amounts of P, Sn, As, and Sb are very low. The easiest method is the measurement of intercept lengths of straight test lines in the phase of interest, as described in paragraph Each micrograph should contain at least? However, if the grains exhibit anisotropy, that is, they are not equiaxed, the image must be either rotated using a prism to rotate the live video image, or the digitized image can be rotated in memory, or scan lines of several orientations may be used, depending upon the capabilities of the image analyzer used.
Fix each micrograph to the tablet surface, for example using masking tape, to prevent movement during analysis.
When using a live microscope image and an eyepiece reticle, simply select more? If measurements were made using only the longitudinal plane, determine the mean value of the measurements.
In most cases except for thin sheet or wire specimensa minimum polished surface area of mm2 0.
L, or the mean grain boundary intersections per unit length, P? These devices relieve much of the tedium associated with manual measurements, thus permitting collection of a larger amount of data and more extensive sampling which will produce better statistical de?
When working with a new alloy composition or a new etchant, it may be helpful to measure the grain size as a function of etch time, or other experimental conditions, to develop a reliable practice 10 that agrees with manual determination of the grain size in accordance with Test Methods E Measure entire area of the largest observed grain section. Measure the area of this grain, Amax, by selecting it with a light pen, mouse, or track ball. Calculate the grain size number based on the mean of the measurements using Table 2 or sstm equations in Table 3.
Measure the entire area of the largest observed grain section.
The grain elongation ratio, or anisotropy index, AI, is de?