Lab 1 Metallographic
pdf
keyboard_arrow_up
School
California State University, Long Beach *
*We aren’t endorsed by this school
Course
361
Subject
Aerospace Engineering
Date
Dec 6, 2023
Type
Pages
7
Uploaded by NuclearNacho48
California State University, Long Beach
Department of Mechanical and Aerospace Engineering
Fall 2023
Lab Report
By
Group Partners:
Experiment Number: 1
Date of Performed: August 23, 2023
Title:
Metallographic Observation and Analysis and Hardness Testing
Course Number: MAE 361
Section Number: 1
Class Number: EN 4 Room 125
Instructor:
Dr. Shamim Mirza
Objective:
To observe the microstructures of engineering materials, grain size, shape & distribution.
Additionally, it is our objective to measure the hardness of engineering materials utilizing the
Rockwell hardness test.
1
Apparatus:
Figure 1
(Polisher Machine: Pace Technologies PENTA-5000 5-Station Hand Grinder)
Figure 2
(Hardness Testing Machine: United Tru-Blue II Rockwell Hardness Tester)
Figure 3
(Grinder-Polisher: Pace Technologies NANO 2000T Circular Grinder-Polisher)
2
Figure 4
(Rockwell Hardness Diamond Indenter & 1045-Steel Sample)
Samples:
1045-Steel Sample
Procedure:
Initially, the PENTA-5000 is used to sand the Steel sample. The PENTA-5000 machine is
turned on along with the water rinse system. Starting at the end face of the sample, the 320-grit is
utilized to smooth the surface. Importantly when sanding, the sample is moved in a circle pattern
to smooth the entire surface area. These steps are repeated with 400, 600, and 1200-grit with a
90-degree rotation after each iteration. Along with the use of NANO 2000T to rinse the surface
to remove any excess material. The Steel surface is then transported to the Tru-Blue II Hardness
Tester. Utilizing the Rockwell Hardness Diamond Indenter, three measurements are taken at
different points of the Steel surface, and the hardness is recorded.
Test Results:
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Indent Trial
Hardness
1
89
2
90
3
85
Hardness Average (μ):
89+90+85
3
= 88
Standard deviation:
HRFS
Σ|𝑥−µ|
2
?
=
14
3
= 2. 16
Utilizing the intercept method to estimate the average grain size, the number of grains
intersected by each of the lines would need to be counted. Note that the magnification of the
grain is 100X and the length of the line is 60mm
.
Number Line
Number of Grains Intersected
1
11
2
10
3
9
4
8.5
5
7
6
10
7
8
Total Line number
Total Grain Number (Length of Line)
7
63.5
Calculating for grain size:
4
(?????? ?? ?𝑖???)(?????ℎ ?? ?𝑖??)
(????? 𝐺??𝑖??)(????𝑖?𝑖???𝑖??)
=
(7)(60)
(63.5)(100)
= 6. 614 × 10
−2
??
Estimating the ASTM grain size would focus on the number of grains in the square
The formula conveys that the average grain size is symbolized by “n”, where it correlates
to the number of grains per square inch, labeled “N”. Note that the image is magnified 100x.
Observing the image, the number of grains is approximately 10, yielding a formula to calculate
the average grain size.
𝐴??? ???𝑖? ?𝑖𝑧?: ?
=
???(?)
???(2)
+ 1 →
???(10)
???(2)
+ 1 = 4. 3
Results and Discussion:
To observe the microstructure of the material it was imperative to calculate grain size--
the following results were as expected. Utilizing the intercept method, the values corresponding
to the number and length of lines, as well as the total grains and magnification, we calculated an
actual
grain size of 0.0614 mm. Taking the
log
of the number of grains and dividing that by
log
(2), derived an ASTM grain size number
n
of 4.3. The grain size has a measurable effect on
most of the mechanical properties it possesses. With a value depicting a
fine
grain size, entailing
more grain boundaries, it can be determined that the observed material sample is generally high
strength.
Answers to Questions:
1. What is the hardness and how is it measured?
A material's resistance to deformation, indentation, or scratching when subjected to an
applied force or load is determined by its hardness. Scratch, indentation, and rebound hardness
tests are the three different types of hardness tests. Indentation hardness refers to how quickly a
sharp tool (referred to as an indenter) is pressed into the material. The mark is larger when it
enters fast. Rockwell, Vickers, and Brinell hardness tests are used to measure indentation
hardness. We utilize a pointed instrument with a diamond tip, such as a cone or sphere, for the
Rockwell test. The indenter in the Vickers test resembles a pointy-topped, straight-sided
pyramid. We employ a metal sphere for the Brinell test. It gets pushed into the material under a
5
specific force. The shape of the indenter matters because it affects the size of the mark left
behind. The hardness value we get is based on how big that mark is.
2. Why are some of the reasons that will cause inaccurate hardness measurement? Name three.
Surface Roughness: Measurements of hardness may not be accurate if the surface of the item
being evaluated is rough or uneven. Variations in the indentation depth can occur from surface
irregularities and produce unreliable results.
Inaccurate Calibration: To provide accurate measurements, hardness testing equipment and
instruments must be correctly calibrated. Results may not be accurate if they are not calibrated
appropriately or frequently.
Uneven Material: The hardness of some materials varies throughout their whole structure.
Hardness measurements may be inaccurate if the substance under test exhibits changes in
hardness at various points.
3. Why are different hardness tests and scales required?
Scratch hardness, indentation hardness, and rebound hardness are the three basic categories of
hardness. We have three sets of tests and measuring scales to go along with these three
categories.
Scratch Hardness: Using tests like the Mohs test, we may determine scratch hardness. We
employ scales such as the Mohs, Ridgway, and Wooddell to determine scratch hardness.
Indentation Hardness: Rockwell, Vickers and Brinell tests are used to measure indentation
hardness. These tests each have a unique set of measurement scales.
Rebound Hardness: Tests like the Leeb test are used to determine rebound hardness. There are
various measuring scales for rebound hardness, just like there are for indentation hardness. We
may better grasp how materials resist scratching, indentation, or rebounding by understanding
how these three hardness kinds relate to three separate sets of tests and scales.
Conclusion:
The major objective of this lab was to satisfy two objectives. First to analyze the
microstructure of engineering materials, and second, to assess whether these materials' hardness
was effectively met. We learned useful skills for using tools like the microscope, grinder
polisher, and hardness testing system throughout the lab. We used a variety of methods to use
metallographic observation and analysis to determine the grain size of the offered samples.
Several changes to the experiment could be taken into consideration. For instance, offering a
variety of cylinders constructed of various materials would provide for a more thorough
understanding of material behavior during hardness testing. To achieve sharper grain images
under the microscope, the polishing process must also be improved because the hand grinder
might not be adequate to produce the appropriate surface quality. Finally, examples of adequately
polished surfaces and excellent microscopic pictures could be provided as useful references to
ensure that specimen preparation is adequate.
6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
References:
1. Ehsan Barjasteh and Parvin Shariat (Editors), MAE 361 Materials and Properties Laboratory
Manual,
Mechanical and Aerospace Engineering Department, CSULB, January 2018.
2. William D. Callister, Jr. & David. D. Rethwisch, Materials Science and Engineering: An
Introduction, any
Edition, Wiley, 2010.
7