Lab Report Template
Lab 1 ‐ Metallography
1. Summary
Experiment Objective:
The objective of this experiment was to conduct a comprehensive metallographic analysis of
various metal samples, including pure metals, solid solution alloys, steels, and cast irons.
Through precise sample preparation techniques involving mounting, grinding, polishing, and
etching, we aimed to uncover and document the internal microstructure of these materials. By
using metallographic microscopes, we examined the samples at both low and high
magnifications, enabling the identification of different phases and the construction of each
metal. Additionally, we sought to estimate grain sizes and examine the relationship between
microstructure and material properties.
Results and Conclusions:
Our examination of the microstructures yielded valuable insights into the nature of the metal
samples. We identified distinct phases within each material, such as ferrite and pearlite,
depending on the sample type. This analysis allowed us to draw connections between
microstructure and material properties. Notably, we observed that variations in composition and
carbon content influenced the microstructure, which in turn affected properties like hardness,
tensile strength, and ductility. Additionally, the successful identification of an unknown sample
through microstructural analysis showcased the practical applications of metallography in
materials science and engineering.
2. Results and Observations
2.1 Record the etching response time for each sample in the table provided
Sample
SAE 1020
SAE 1045
SAE 1080
Iron Ingot
Etch Response Time (Seconds)
10-20s
10-20s
13s
25s
2.2 Attach the micrographs of the four samples in the space provided. Indicate the magnification and label all
phases present. Record additional observation in the space provided (e.g., differences between the
microstructure of these samples).
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Sample #1 ‐ Ingot Cast Iron Micrograph
Additional Observations
In ferrite
phase sine
theres low
carbon
content
No substantial
black grains –
impurities or
low carbon
Sample #2 ‐ SAE 1020 Steel Micrograph
Additional Observations
Both black and white
grains.
White grains are
ferrite and black
grains are pearlite.
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Sample #3 – SAE 1045 Steel Micrograph
Additional Observations
Mostly pearlite in this
section it seems.
Ferrite phase grains
are large.
Sample #4 ‐ Unknown Sample Micrograph
The
SAE 1080
Additional Observations
Mix between
black
cementite and
white ferrite.
All grains in
pearlite phase
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2.3 Calculate the grain size (grain diameter) of Sample #1 (the ingot cast iron). Take three
measurements and show your grain size calculation in the space provided.
(17.674 + 7.579 + 11.087)/3 = 12.11 μm
3. Provide answers to the questions given by the TA and attach them to the end of this
template.
Discuss what pearlite and ferrite looks like under the microstructure and list their properties.
Pearlite and ferrite are two microstructural components commonly found in metals, especially in steel.
Pearlite has a layered structure with alternating light (ferrite) and dark (cementite) bands, resulting from a
eutectoid reaction during cooling. It is intermediate in hardness, contributes to strength, enhances
ductility, provides toughness, and has moderate electrical conductivity.
Ferrite, on the other hand, appears as a bright phase with a cubic crystal structure (body-centered cubic
or BCC). It is relatively soft, highly ductile, ferromagnetic, and offers good electrical conductivity. Some
stainless steel alloys contain ferrite for corrosion resistance.
Discuss the effect of grain size on the strength and toughness of the material and explain why
The grain size of a material significantly influences its mechanical properties. Smaller grain sizes lead to
increased strength through grain boundary strengthening and the Hall-Petch relationship, as finer grains
create more obstacles to dislocation motion. Conversely, larger grain sizes tend to enhance toughness and
ductility, allowing for more plastic deformation and energy absorption during fracture, reducing the risk of
brittle failure. The interaction between dislocations and grain boundaries explains these effects, with
materials containing finer grains being stronger but potentially more brittle, while those with larger grains
offer improved toughness and ductility.
Compare carbon content vs microstructure, their relation, and discuss the effect of increasing carbon
content in the material and how it affects the microstructure.
The relationship between carbon content and microstructure in materials like steel significantly impacts
their mechanical properties. Low-carbon steel (up to 0.3% carbon) is soft and ductile due to its ferritic
microstructure. Medium-carbon steel (0.3% to 0.6% carbon) transitions to pearlite, offering a balance of
strength and ductility. High-carbon steel (above 0.6%) becomes hard but brittle with cementite
dominance, while very high carbon levels (above 0.8%) yield extremely hard but brittle martensite.
Engineers choose materials based on this relationship, selecting low carbon for ductility and toughness,
and high carbon for hardness and wear resistance, while considering trade-offs between these properties
for specific applications.
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