Laporan Akhir Praktikum

Analisis Struktur Material

Nama : Kent Chester

NPM : 1306437252

Kelompok : II

Laboratorium Metalografi dan HST

Fakultas Teknik Universitas Indonesia

2014

CHAPTER 1 SAMPLE PREPARATION

1.1 Cutting

This process was not done and we skipped into mounting directly.

1.2 Mounting

1.2.1 Purpose of mounting

Mounting is a method of placing a sample in a media in order to ease handling the

small size and irregular shape of the sample without damage it.

The small-sized specimen or specimen that does not have regularity form will be

hard to be handled, especially when they are on the stage of grinding and polishing.

This happens in specimen such as wire, thin metal sheet, thin cut etc. These

specimen must be placed in a media (mounting media) to ease the handling. In

general the requirements that mounting media must have are:

-It should be inert (unreactive to the material and the etching solution)

-It has low exothermic

-It has low viscosity

-It is adhesive

-It has the same strength with the sample

-It has good flowability, is able to get into the irregular pore, hole or cavity that

exist in the sample

-Especially to electroetching and SEM testing, the mounting media must be

condusive.

Mounting media is made of resin and hardener. The process was done by the lab

assistant. The resin in liquid form was added until it reaches less than half a cup for

hardening the resin hardener is added for about 15 drops. The mixture is then left

until it hardens. Time depends on the quality of the hardener used.

1.2.2 Tools and Materials

-Small cylindrical object for the base.

-resin

-hardener

-tape

1.2.3 Flowchart of the process

1.2.4 Analysis of individual sample mounting

The Results of mounting is good, we have been introduced how to mount the

specimen carefully with resin and hardener, but because of the time needed to wait

is too long, so we can just see the result. The results is a non bubbled Al-Si that have

a good makrostructure that can easy to do the Sample preparation.

1.2.5 Analysis of group sample mounting

The Sample mounting of the other specimen is good too, the parameter of how good or not is based on how the specimen not being damaged or have any defects on it.

1.3 Grinding1.3.1 Purpose of grinding

In view of the perfection required in an ideally prepared metallographic sample, it is

essential that each preparation stage be carefully performed. The specimen must:

Take small hollow cylindrical object.

Pour resin until it is 1/3 full.

Add hardener and the sample

Leave the mixture until it hardensDONE!!!

1. Be free from scratches, stains and others imperfections which tend to mark the

surface.

2. Retain non-metallic inclusions.

3. Reveal no evidence of chipping due to brittle intermetallic compounds and

phases.

4. Be free from all traces of disturbed metal.

The purpose of the coarse grinding stage is to generate the initial flat surface

necessary for the subsequent grinding and polishing steps. In the experiment we

used many abrasive papers with different units ranging from 80-1000. The 80 with

the highest abrasive power.

1.3.2 Tools and Materials

Abrasive paper

Sample

Water

Rotating grinding machine

1.3.3 Flow Chart

1.3.4 Analysis of individual sample grinding

Remove the cover of grinding machine and

put abrasive paper.

Close it back, start the machine with the

desired speed and place the object.

Add water periodically to

remove friction.

Keep grinding until the required surface

is achieved.DONE!!!

By grinding the AlSi, we can know the differences of Abrasive paper and how it can

do or affect the specimen we want to grind. AlSi can be easily grinding, it just need

one or two minutes to finish the grinding.

1.3.5 Analysis of group sample grinding

The other materials, like Low Carbon Steel and CuZn is harder to grind for. It can be

grind, but need extra effort to make the specimen lost it straight parallel line on it.

1.4 Polishing1.4.1 Purpose of polishing

Polishing is the most important step in preparing a specimen for microstructural

analysis. It is the step which is required to completely eliminate previous damage.

Ideally the amount of damage produced during cutting and grinding was minimized

through proper blade and abrasive grinding so that polishing can be minimized.To

remove deformation from fine grinding and obtain a surface that is highly reflective,

the specimens must be polished before they can be examined under the microscope.

Polishing is a complex activity in which factors such as quality and suitability for the

cloth, abrasive, polishing pressure, polishing speed and duration need to be taken

into account. The quality of the surface obtained after the final polishing depends on

all these factors and the finish of the surface on completion of each of the previous

stages.

1.4.2 Tools and Materials

Chemical (aluminum oxide)

Water

Rotating polish machine

1.4.3 Flowchart

1.4.3 Analysis of individual sample polishing

Eventhough AL Si is easily grinded, but it is harder to being polished. It takes time to

make all the straight line disappeared.

1.4.4 Analysis of group sample polishing

In the other hand, Low Carbon High Temperature Sttel, have a more chance to be a

full polished materials, it looks like a mirror.

1.5 Etching 1.5.1 Purpose of etching

Metallographic etching is the process of revealing microstructural details that would

otherwise not be evident on the as-polished sample. Etching is not always required

as some features are visible in the as-polished condition such as porosity, cracks and

inclusions. A properly prepared specimen will reveal properties such as grain size,

segregation, and the shape, size, and distribution of the phases and inclusions that

are present, while other aspects such as mechanical deformation and thermal

treatments may also be able to be determined.

1.5.2 Tools and Materials

Sample

Take sample after grinding

Turn on the polishing machine

Add chemical and water periodically

Polish the sample until the scratches

are goneDONE!!!

Chemical used (Hydrofloric acid, picral, nital, Ferric Chloride)

Dryer

1.5.3 Flowchart

1.5.4 Analysis of individual sample etching

In Etching, the HF is added into the etching process, for 15 times etch, and alcohol

helps, it create a good etch for AL Si

1.5.5 Analysis of group sample etching

Not all of the etching is success, there are a overethcing and underetching, the

microstructure after the checking is differ too.

Take sample after polishing

Clean the sample with water

Prepare the chemicals as required by the

sample

Dip the sample for certain period of time

and then dry itDONE!!!

Chapter II

Micro and Macrostructure Photos Observation and Analysis

II.1 Objective

a. Analyze the micro and Macrostructure and properties.

b. Recognize the phases in the microstructure.

c. Calculating the phase percentage and grain size using manual or “Image Analyzer”

software.

d. Knowing the process of capturing images of microstructures

II.2 Tools and Material

a. Preparation Sample after Etching (Specimen : AlSi, High Temperature Steel, Carbon

Steel, NiCu)

b. Microscope

II.3 Flowchart Process

II.4 Photo and Makrostructure Analysis

II.4.1 Photos of Makrostructure and Comparation with literature

Discussion of photomicrograph

Prepare the specimen

Use Olympus Microscope on the

Specimen

Observe the Specimen

Sketch the basic microstructural

features

Identify the features on

photomicrographs

Al-Si 200x

AlSi Literature

Cu 50x

Cu Literature

II.4.2 Photo Makrostructure Analysis Experiment Vs Literature

For Aluminum, The Colour is White and Blue, it is can be forged, tough, have a light

mass. In the Makrostructure, it seems like a ceramics, have a lot of grain and in the

experiment, the results is not too good, because it still left the parallel lines. Not like the

literature the microstructure is not with any parallel lines. (line defect)

For Copper, the material characteristic is not too far than the Alumunium. The

differences is just copper more heavy than Al.

In the otherhand, the Copper, in the literature, have lots of defect and Void in the

experiment photos, but it also happen in the literature eventhought the quantity is small.

II.5 Photo dan Analysis Sampel Mikrostruktur

II.5.1 Photo Analysis Structure

Low Carbon 500x

Low Carbon Literature

Martensite 500x

II.5.2 Analysis Photo Mikrostructure Experiment vs Literature

For the Low Carbon, the material is no more ductile if we compare it with the

martensite materials. In the low carbon one, the experiment show that it still have left the

line defect, also have lots of void across the center granular. It show how the low carbon

have a little ductile. It seems that in the literature, it’s more a ductility phases than the

experiment.

For the martensites, the material is in the martensite phases. So the material must

be so sharps like the literature. But, in the experiment, it cannot be seeing clearly because

of overetch and the line defect is too big.

CHAPTER 3: JOMINY AND HST TEST

3.1 JOMINY TEST

3.1.1 DATA AND GRAPHIC OF JOMINY TEST

a. Data

Distance From Quenching Media

(mm)Hardness

(HRB)6 93

12 90.421 92.429 93.634 72.745 87.151 81.260 83.768 79.871 78.2

b. Graphic

0 10 20 30 40 50 60 70 800

10

20

30

40

50

60

70

80

90

100

Hardness (HRB)

c. Example of Calculation

BHN Formula: BHN= 2⋅P

( p⋅D)(D−√D2−d2 )We didn’t have any example calculation since the lab assistant did it for us.

3.1.2 DATA AND GRAPHIC ANALYSIS OF JOMINY TEST

The data shows the fact that the further the distance from the quenching media, the

smaller the hardness of a material will be (HRB). In this review paper we have studied the

importance of Jominy test in metallurgy and change in hardenability of different steels due

to change in alloying elements in steels using jominy test. We have noticed that their

variations are related to micro structural change. We have studied standard graphs of

Jominy test for various steels. The data from Jominy test can be used to determine whether

particular steel can be sufficiently hardened in different quenching media, for different

section diameters.

Heat treatment given to a type of material greatly influence the final mechanical

properties of the material. Therefore the heat treatment, sometimes with different

purposes, there is increasing violence, or some are even actually aimed at increasing

toughness with little expense violence. Therefore, to analyze the final properties of the

material should be considered heat treatment they experienced.

Combination of heating and cooling process that aims to change the microstructure

and mechanical properties of metals called heat treatment. Jominy testing has been

standardized by ASTM, SAE, and AISI. After the samples were heated up to 920oC, the

sample will be cooled in running water. Samples will respond to cooling required. The

bottom of the sample by flowing water will experience the most rapid cooling and the

bottom will be formed up which called martensite phase and the top is ferrite phase.

Martensite phase indicates that the sample has a hardness level of the loudest. Instead

ferrite phase showed the most lenient level of violence among other phase.

The faster the rate of cooling, the martensite is formed will be more and the nature

of violence will be higher. And the longer the cooling rate, the chances of the formation of

martensite would be even smaller. This is because in the sample had a slower cooling rate

of diffusion of carbon which lead to the formation of phase ferrite, pearlite, or bainite

where these phases have a lower hardness than martensite phase.

Variables that can affect this experiment include:

a. Austenisation temperature and time

If the temperature is reduced, then there is no hardness. And if the time

required becomes excessive, then the grain growth and the toughness to be poor

or fragile. If the austenite temperature is high, it will get a large austenite grains.

Meanwhile, when the austenite temperature is low, it will get small grains. The

effect of austenite temperature is not only for grain growth, but also for

hardness. The high temperature will result the higher hardness. This is due to

the high austenite temperatures which will assist carbon dissolved in austenite

and will transform to martensite because levels of carbon trapped in the crystal

structure is more. Whereas with lower temperatures, it will not produce

maximum hardness.

b. The speed of cooling

If the speed cooling is fast, then the hardness gained will be harder.

Conversely, if the cooling is done by a long, well-formed phase will not be too

hard.

Jominy experiment aims to determine how much material has martensite phase,

predict how the hardness is achieved, and compare the hardness of a material with its

standard. Jominy curve can be determined by the relationship between the speed of the

cooling phase is formed and get violent nature.

3.2 HST TEST

3.2.1 DATA RESULTS AND COMPARISON WITH OTHER GROUP

Media: Water

Group 1.

Hardness

(HRB)

86.4

86.2

88.6

Media: Air

Group 3.

Hardness

(HRB)

72.8

81.7

82.9

Media: Oil

Hardness

(HRB)

108.1

109.2

109.9

Calculations:

The Hardness test was using ASTM E18 – Standard test method for Rockwell Hardness

Testing. ASTM E18 is a method of determining hardness by measuring how deep an

indenter pushes into a metal under a given load. We know that Rockwell Hardness Testing

did not use particular calculation, which means the machine did all the work.

3.2.2 TESTING ANALYSIS

We group two, we use water as the media for Heat & Surface Treatment. Group one

use air as the media and group three use oil as the media. Based on the result above, we can

conclude that water is the best media for heat and surface treatment test since the average

of hardness resulted is much greater than when using oil and air only.

In heat treatment, there are many ways of doing the experiment. Heat treatment

techniques include annealing, case hardening, precipitation strengthening, tempering

and quenching. In this test that is done by three groups, two techniques were used for

doing the test. The techniques are the annealing and quenching techniques.

Group one uses the annealing techniques which was the normalizing. Normalizing is

a technique used to provide uniformity in grain size and composition throughout an alloy.

The term is often used for ferrous alloys that have been austenitized and then cooled in

open air. Normalizing gives harder and stronger, even though not more ductile steel. Group

one uses this techniques and have the average results of hardness which is 87.067.

Group three uses the quenching technique and using oil for cooling media or

quenchant. To harden by quenching, a metal must be heated above the upper critical

temperature and then quickly cooled. Depending on the alloy and other considerations

(such as concern for maximum hardness vs. cracking and distortion), cooling may be done

with forced air or other gases, (such as nitrogen). Liquids may be used, due to their

better thermal conductivity, such as oil, water, a polymer dissolved in water, or a brine.

Using the same technique as our group, but with different media, group three have the

hardness average result which is 79.13.

Our group have the average result of 109.067 HRB. With all this results, our group

have the largest average of hardness. From the analysis this group have made, we reach the

analysis that between these two techniques, none have advantages since the data is very

limited. But from the data we can gathered, since we have the largest results of hardness, it

means that using quenching with water is one of the better ways to harden a metal.

Bab 4

Conclusion

III. Conclusion

III.1 Conclusion

The experiment of metallography is based on how we wanted to recreate the

material we wanted by checking its ductility and brittleness, we can find it by conducting a

sample preparation process and also Microsctructure observation process. The other

experiment like jominy experiment also conclude the same conclusion but with different

way and different purposes, that is to see the quenching of material phase.

III.2 Critism

The experiment is already good, but still need lots of improvement like how to take

a photos in the microscope, how to mounting, how to heat treatment but each process need

to be observe if it’s important.

Reference

15483 ITSundregraduate.pdf

Mmodul.mesintalic