Microanalysis Lab - Professor Samardzic PDF

Preview

Summary

Professor Samardzic...

Description

1

MECHANICAL ENGINEERING LABORATORY NEW JERSEY INSTITUTE OF TECHNOLOGY

Report Submitted by

Emily Carvalho

Date Performed

2/20/20

Course & Section

ME215-004

Experiment No.

Date Submitted Instructor

2/27/20 Professor Veljko

MICROANALYSIS

Performed by Group

Group Members

001A

With TA

Paul Mamauag Mohamed Diab (Leader) Kai Cha Ramazan Uku

Yassine

2

2

TABLE OF CONTENTS Abstract

3

Introduction

3

Procedure

3

Original Data Sheet

4

Results and Calculations

5

Discussion

7

Conclusion

7

Questions and Answers

8

References

10

3

Abstract This laboratory is focused on understanding the relationship between microstructures of materials and their resulting mechanical properties. The purpose of the lab was to observe the microstructures of the prepared specimens and then determine which material it was. We were split up into 2 groups: one group went to the television microscope and the other went to the regular microscopes. We took turns on each of the microscopes determining which specimen was which. Afterwards we then researched the mechanical properties of the materials examined. The result of this lab was an understanding of the basics of microstructures and properties and a use of optical microscopes (with television screens and without), eyepiece micrometer, and 6 different prepared specimens.

Introduction This laboratory exposed students to how materials are prepared for examination of their microstructures and then allowed students to observe microstructures of materials already prepared. The main objectives of this lab was to 1) experience a brief overview of the process of surface preparation and etching, 2) learn how to utilize an optical microscope, 3) recognize and draw the observed microstructures, and 4) Identify the mechanical properties of the 6 materials given. The term microanalysis has only been around for a little over a century but the study has been progressing for hundreds of years. It wasn’t until late 19th century that microanalysis became similar to what is done in this lab (Hillis, 1945). This lab is extremely important because engineers work with different materials everyday and understanding their properties is vital to safely using and applying them.

Procedure 1. Turn on the television microscope and make sure the magnification is at 200x 2. With each specimen, adjust the table and magnification to get a clear image 3. Using a usb, save an image of the microstructure for each specimen

4

4. Identify each microstructure as one of the six materials given: hypereutectoid steel, hypoeutectoid steel, aluminum bronze, gray cast iron, white cast iron, nodular cast iron 5. Using the manual microscopes, repeat the process, but draw each microstructure on the data sheet 6. Fill out Table 2

Optical Microscopes Eyepiece Micrometer 6 prepared specimens

5

Original Data Sheet

- Optical Microscopes - Eyepiece Micrometer

6

Results and Calculations

Aluminum Bronze (E8)

White Cast Iron (M12)

Nodular Cast Iron (NG1)

Hypereutectoid Steel (N15)

Hypoeutectoid Steel (N20)

Gray Cast Iron (M6)

Of the 6 materials given, N20, N15, NG1, M6, M12, and E8, we concluded that each were the specific metals we wrote above with the corresponding number.

7

NG Image Analyzer showing the different components of the analyzed material TABLE 2. Properties of the Metal Examined Mechanical Properties Materials or Alloys

Ultimate Tensile Strength (psi)

Yield Strength (psi)

Elongation %

Hardness (Brinell)

Modulus of Elasticity (psi)

Aluminum Bronze

74,700

29,700

12

170

1.6x107

good

White Cast Iron

50,000 99,931

70,100

1-10

350-807

2.33x107 3.481x107

good

Nodular Cast Iron

>= 65,000

>= 45,000

12

131-220

2.4x107 2.6x107

good

Hypereutectoid Steel

23,300 464,000

39,900 484,000

.5-30

163-600

2x106 3.41x107

good

Hypoeutectoid Steel

63,800

53,700

15

126

2.97x107

good

Gray Cast Iron

16,700 102,000

9,500 25,000

1-15

120-550

9,000 23,500

poor

Machinability

Discussion This laboratory was extremely informative on the process of how microstructures are

8

observed by the naked eye and under a microscope. Every material has a unique structure, however, there is a distinct pattern that can be used to determine the type of material and what it is made of. We learned how to identify the samples we were given out of the 6 known materials and successfully draw the microstructures. To do this, we had to have an understanding of the preparation process and characteristics of the metals. To reiterate, the main objectives of this lab were to 1) experience a brief overview of the process of surface preparation and etching, 2) learn how to utilize an optical microscope, 3) recognize and draw the observed microstructures, and 4) Identify the mechanical properties of the 6 materials given. We accomplished all of these objectives when we watched videos on the procedure of surface etching and preparation, used the microscopes to examine the materials we were given and researched the information to be able to fill out Table 2 on the mechanical properties. As there were no calculations, there were no sources of error for that. However, there was error in researching the mechanical properties of the materials that were given. Every source had variations in the properties and it was very difficult to find consistent data. This was due to the fact that every piece of the “same” material will always be unique to itself, which makes finding universal values impossible.

Conclusion In conclusion, the lab was successful in teaching us how materials are polished, etched, washed, and then dried in a meticulous manner in order to be analyzed. We were then able to apply this by using samples that had already been etched for us and look at their microstructures under the microscopes. The purpose of this lab was to be able to identify which microstructure correlated to the structures of the metals we were given: hypereutectoid steel, hypoeutectoid steel, aluminum bronze, gray cast iron, white cast iron, nodular cast iron. We accomplished all our objectives and worked cohesively as a group to observe microstructure under a microscope and determine which material it was.

Questions and Answers 1) List the commons types of cast iron that can be produced Common types of cast iron are white, gray, compacted graphite, ductile, malleable (Stefanescu, 2017).

9

2) What is the difference between the microstructures of gray and nodular cast iron The difference between the microstructures of gray and nodular cast iron is that nodular cast iron is stronger, more ductile, and has a higher elongation (Stefanescu, 2017). 3) Describe the difference between bronze and brass. Define these two alloys and give some detail of these alloys The difference between the two is that bronze describes copper alloys with an addition of tin and brass is a copper alloy with a primarily zinc addition. Bronzes are not as “readily fabricated” as brasses and have less percent elongation (Ali, 2016). Brasses are not as electrically conductive and have poor corrosion resistance but have higher strength than bronzes (Ali, 2016). 4) What is the chemical composition of 4340 steel? Assuming this steel is to be used as a member in an aircraft assembly, what mechanical properties would be desirable for this application? Carbon: 0.38-0.43 Manganese: 0.60-0.80 Phosphorus (Max): 0.035 Sulfur (Max): 0.040 Silicon: 0.15-0.35 Nickel: 1.65-2.00 Chromium: 0.70-0.90 Molybdenum: 0.20-0.30 Assuming this steel is used for aircraft assembly, its mechanical properties of deep hardenability, strength, toughness, and resistance to fatigue and creep are what make it desirable for this application (Philip, McCaffrey, 1990) 5) What are the main constituents of a medium carbon content alloy steel at room temperature? Medium carbon content alloy steel is made up of Carbon and and Manganese at room temperature (Singh, 2016). 6) Make sketch of pearlite grain and label pearlite components

7) Does pearlite contain some portion of cementite? If yes, sketch how pearlite looks and identify the constituents. Yes, as shown above in the sketch in question 6, pearlite contains cementite (12.5 wt%) and ferrite (87.5 wt%)

10

8) Is it possible to weld a plain carbon content steel (1025)? Plain carbon content steels can be welded with nearly no special measures to prevent cracking (Liu, Indacochea, 1990). 9) Is it true that aluminum is known for its excellent thermal conductivity? Name two additional characteristics of aluminum. Yes, it is true that aluminum is known for its excellent thermal conductivity. It is also very flexible and has a high strength-to-weight ratio (Kissel, 2019). 10) Describe the influence of different grain size on mechanical properties (ductility, tensile strength, and hardness) Smaller grain sizes yield less ductility, higher tensile strength, and higher hardness. Larger grain sizes yield more ductility, lower tensile strength, and lower hardness.

References Ali, Sabit. (2016). Heat Treating of Bronzes. In ASM Handbook (Vol. 4E), 355-396. https://doi.org/10.31399/asm.hb.v04e.a0006281 Ali, Sabit. (2016). Heat Treating of Brasses. In ASM Handbook (Vol. 4E), 335-354. https://doi.org/10.31399/asm.hb.v04e.a0006280 Black, J., & Kosher, R. (2017). DeGarmo's Materials and Processes in Manufacturing(12th ed.). Hoboken, NJ, USA: Wiley. Hillis, Mary O. (1945) The history of microanalysis. Journal of Chemical Education, 348. https://doi.org/10.1021/ed022p348 Liu, S., Indacochea, J.E. (1990). Weldability of Steels. In ASM Handbook (Vol. 1), 603613. https://doi.org/10.31399/asm.hb.v04e.a0006280 Philip, Thoni V., McCaffrey, Thomas J. (1990). Ultrahigh-Strength Steels. In ASM Handbook (Vol. 1), 430-448. https://doi.org/10.31399/asm.hb.v01.a0001027

11

Stefanescu, Doru M. (2017). Classification and Basic Types of Cast Iron. In ASM Handbook (Vol. 1A), 12-27. https://doi.org/10.31399/asm.hb.v01a.a0006294 Singh, Ramesh. (2016). Applied Welding Engineering (2nd Edition), Butterworth-Heinemann, 57-64, https://doi.org/10.1016/B978-0-12-804176-5.00006-2. Kissell, J. Randolph. (2019). Aluminum Structural Design. In ASM Handbook (Vol. 2B), 19-32. https://doi.org/10.31399/asm.hb.v02b.a0006486...