Grain Size Measurement Methods.

How to calculate ASTM grian size of microstructure which have a scale bar?

Grain size analysis is used as a quality control tool to ensure that alloys are manufactured to specification. Some examples of this include verification of the heat treatment and condition of the alloy. It can also be used to assist in understanding material failures.

I have to find ASTM grain size, I would like to know is it a correct way to find the exact magnification of microstructure using scale bar .

We have the microstructure test specimen of various metals at the lab. I used those microstructure test specimen to calculate the grain size using the

Formula N*=2exp(n-1)

at magnification of 100 X measured in an area of 1 sq. inch. I want to know if it is the standard method for obtaining the average grain size. Can anyone attach the American Society for Testing and Materials document ASTM E112-12?

Calculation of ASTM Grain Size Number?

Example:-

Supposed we count 16 Grain per square inch in a photomicrographs Taken at magnafication ×250 what is the ASTM grain number.

If we count 16 grains per square inch at magnification x 250,

then at magnification x 100 we must have:

N=(250/100}²* (16) = 100 grains/in.²=2ⁿ − 1

Log 100 = (n ~ 1) log 2

2= (n 1)(0.301)

n=7.64

Chemical Etching Process?

Take100 ml D.M.water and heat 70~80 °C and added picric acid 5Gm and sodium dodecylbenzene sulfonate ( C18H29NaO3S ) and continue mixed by and Glass rod.

Then add High carbon steel as like En8D and other for some time ( 1 Minute) for mixed carbon alloyment.

Then added 3ml Hydrogen peroxide (H2O2)slowly slowly in chemical , bobble are showing on upper surface in chemical solution.

The chemical solution is ready for eatching of specimens.

Surfaces clean side of specimens drop in chemical solution for 1~3 minutes and after completing the process wash with clean water.

Then check 100×

Thanks.

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