Materials - LAB 1

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Muhammad Khairuddin Bin Zaidy

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EMD 4M5

3.0 Experimental Procedure

In this experiment, we as students were demonstrated about the basic procedure in

metallurgical studies in terms of preparation of samples for metallographic observation

and basic operation of optical microscope. Every step was demonstrated clearly in terms

of its operation and purpose.

4.0 Findings

4.1 Find out why microstructures study is important in materials science especially in

engineering field?

Microstructure study in materials science is important because everyday many

applied scientist or engineer encounter problem or task involving materials. Selecting the

appropriate materials could be the factor between success and failure of the task.Although the materials look all the way same roughly, but under microscopic view the

properties of materials could be different.

4.2 Explain why there are many types of etchant used in microscopic examination of

metals? Give at least 3 types of etchants, their chemical composition and their purpose.

Also explain what make one etchant differences to another?

There are many type of etchant used in microscopic examination. This is because

different type of metals contains different type of composition. Thus we have to use

different type of etchant for different composition. Example:

Etchant Chemical Composition Purpose

NitalEthanol : 100 ml

Nitric acid : 1-10 mlMost common etchant for

Fe, carbon and alloys steels

and cast iron

PicralEthanol : 100 ml

Picric acid : 2-4 grams

Recommended for

microstructures containingferrite and carbide.

Vilellas ReagentGlycerol : 45 ml

Nitric acid : 15 ml

Hydrochloric acid : 30 ml

Good for ferrite-carbidestructures (tempered

martensite) in iron and steel

Kalling's No. 1

Distilled water : 33 ml

CuCl2 : 1.5 grams

Hydrochloric acid : 33 mlEthanol : 33 ml

For etching martensitic

stainless steels. Martensite

will be dark and the ferritewill be colored.

4.3 How do different phases exist in an alloy during microstructure studies?

Different phases exist in an alloy during microstructure studies if cause by

different type of treatment that been apply to that alloy.


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5.0 Discussion

5.1 Sample Preparation

A) Cutting

This is the first step in sample

preparation in raw specimen selection.

When the specimen had been choosing, itwill undergo cutting process. This is due to

the physical properties of the specimen, as

example, a rod of aluminum. It is heavy andlong, thus it is hard to study the

microstructure of the aluminum. So, we cut

it into small pieces of rod before molded.There are many type of cutting machine

such as cut-off machine and precisionscutter. Cut-off machine often used in bigsamples, while precisions cutter is used

when we need no cut the samples in very

precise measurement, up to millimeter, by

using diamond-coated blade.

.

B) Molding

In this step, sample that has been cut will be covered by a mean of mounting,

through hot pressing technique. In this experiment, we used Simplimet 2000 Automatic

Mounting Press. 1st, the specimen is positioned on top of the pressing place. Then,

molding material is added to the pressing machine. Next, all details such as temperature,pressure and others is set on the machine. After desired time, the mounting process is

done.

Cutting Machine Technician cutting

the specimen

Automatic Pressing Machine Sample is positioned on machine

Precision Cutter


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C) Grinding

After finished been molded, the specimen then go through

grinding process. There are two types of grinding, rough

grinding and fine grinding. Firstly sample will undergo rough

grinding to remove rough scale and gross imperfections onthe surface. Then, the sample will undergo fine grinding

which will improve the surface of sample and it begins to

shine and reflect light slightly. In this step, we used roughsand paper for rough grinding, then we used smooth sand

paper for fine grinding.

D) Polishing

This process is similar to grinding process, but polishing consists detailing more

the sample. Polishing process also has 2 types; rough and fine. Rough polishing willremove all imperfections that grinding process has left. Then, fine polishing will removeall scratches and leave a mirror like finishing on the surface. In this step, we used very

high number of grade of sand paper, which shows that the sand paper is very-very

smooth.

E) Etching

In this step, we will complete the sample for study by etching the sample.

Etchants are composed of organic or inorganic acids and alkalis dissolved in alcohol,water or other solvent. Various acids and alkalis are used o selectively attack the surfaces

of metals to reveal grain boundaries, phases,

precipitates, inclusions and variations incomposition.

Grinding Machine

Polishing Machine Mirror like finishing

Sample of etchants that been used.


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6.0 Conclusion

After completing this experiment, we can conclude that we understand all thesteps required in preparing metallographic sample, from cutting process until etching

process. We also understand the basic concept of etching. This solvent reacts with the

composition of the specimen, and will help observer to identify the microstructure of thesample, such as grain boundary and others. We also understand the basic function of

optical microscope and how its operate. This can help us in future when we have to

examine microstructure of a specimen. Lastly, we also manage to use and perform


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analysis from the microstructures observed. From this analysis we can conclude several

main points in different task of experiment.

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Materials - LAB 1