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Laboratory Experiment No. 9 Corrosion of Metals

Submitted to fulfil the Requirement of MSE 227L (16636) Monday Nights 7:00 pm -9:45pm California State University Northridge College of Engineering and Computer Science Manufacturing Systems Engineering and Management Coach Tony Magee, MS, MBA 28 September 2020 Adan Munoz Daniel Hernandez Ethan Duarte Prepared by Jose Puentes

Laboratory Experiment No. 9 Corrosion of Metals Abstract: In this Experiment, the properties of cold working on a microstructure were studied from a 70/30 Cartridge Brass. The brass specimen was studied through the testing of its hardness while its constantly being cold rolled up until its thickness was at 50%. Once the brass Specimen was rolled, it was tested at different temperatures to study the effect of temperature in relation to its hardness. Microscopic images of the brass specimen were examined in order to calculate its grain size and to study its relationship with temperature. Introduction: In the cold working process the energy expended in a plastically deformed material such as metal shows an increase in internal energy. Therefore, producing changes in its physical and mechanical properties. Essentially when a material is deformed there are changes in its hardness. At the microstructural level, when the increments of internal energy are increased the dislocation density is affected. At an even more microstructural level there are differences in the grains showing that when they are more elongated, they tend to show an increase in hardness and strength as a result from cold working. So, the purpose of cold working is to see its effect on the material and how it changes its properties. After the cold work, there are three different stages that occur to demonstrate the effects of the cold work and how it effects the hardness. The three-step process is known as annealing, and they are known as recovery, recrystallization, and grain growth. When a material is in recovery, it is usually at a low temperature and involves the rearrangement of dislocations which results the forming of sub grains. In this process the hardness is hardly changed because of the low temperature. The recrystallization process is usually at a higher temperature, almost at melting point of the metal. This is where grains usually start to grow and us due to the dislocations being annihilated. This is also where strength and hardness begin to decrease as the material is gaining ductility. At the highest temperatures the process of Grain Growth occurs, and there is a very low hardness value. The purpose of annealing is that it provides a better insight of how the grain structure looks like so that it can help determine the properties of the material. The measurement of hardness is determined using the Rockwell hardness tester. The Rockwell Hardness tester determines its hardness by applying a load onto the specimen and creating an indentation on the specimen. The load divided by the surface area of the indentation gives you

Laboratory Experiment No. 9 Corrosion of Metals the hardness value. Hardness values should vary between 20 – 100 or else the settings of the Rockwell Hardness Tester may not be properly calibrated. Procedure: 1. To begin this experiment, the initial thickness of the brass specimen must be measured. Once the thickness is measured the brass specimen can now be tested for its hardness on the Rockwell hardness tester. After that, the brass specimen can now be rolled until its thickness is 50% of its original. In between the rolling of the specimen make sure to measure its hardness. 2. After the specimen has been rolled to 50% of it’s initial thickness, measure the hardness one last time. 3. Now cut the brass specimen into 8 pieces measuring about ½ inch long. 4. Once they are cut place them in the hot bath with the following temperatures for about 30 minutes.

5. After heating the brass specimens, quench them in water and measure the hardness values of each of 8 specimens. 6. Lastly analyze its microstructure using the microscopic images of brass. Analyze its grains and calculate its grain size. Only do this for the three highest temperatures.

Laboratory Experiment No. 9 Corrosion of Metals Discussion: Table 1 Hardness In Relation To The Percent Reduction Of Thickness

Hardness Average (HRBW)

27.61

76.87

82.28

84.70

88.36

91.83

Initial Thickness (in)

0.250

0.205

0.192

0.178

0.138

0.125

Percent Reduction Thickness

0%

18%

23%

29%

45%

50%

Table 2 Annealing Temperature and Hardness Average Anealing Temperature (°C)

22

250

300

350

400

500

600

700

Hardness Average (HBRW)

89.10

89.49

83.08

61.58

55.57

48.57

29.03

22.35

Table 3 Grain Size and Temperature ASTM Grain Size (µm) Temperature

10 500

11.85 600

12.32 700

Laboratory Experiment No. 9 Corrosion of Metals Hardness v Percent Reduction 100 90

Hardness (HBRW)

80 70 60 50 40 30 20 10 0 0%

10%

20%

30%

40%

50%

60%

Precent Reduction of Thickness

Figure 1 Hardness vs Percent Reduction of Thickness

Hardness v Temperature 120.00

Hardnesss (HBRW)

100.00 80.00 60.00 40.00 20.00 0.00

0

100

200

300

400

500

600

700

Temperature (°C)

Figure 2 Hardness Vs Temperature Of 50% Cold Worked Brass

800

Laboratory Experiment No. 9 Corrosion of Metals ASTM Grain Size v Temperature 14.00 12.00

Grain Size

10.00 8.00 6.00 4.00 2.00 0.00 450

500

550

600

650

Temperature (°C)

Figure 3 ASTM Grain Size vs Temperature

700

750

Laboratory Experiment No. 9 Corrosion of Metals

Figure 4 Microstructure of Brass at 500 Degrees Celsius

Figure 5 Microstructure of Brass at 600 Degree Celsius

Laboratory Experiment No. 9 Corrosion of Metals

Figure69Microstructure Microstructureof ofBrass Brassat at600 700Degrees DegreesCelsius Celsius Figure

Figure 7 Microstructure of Brass at 700 Degrees Celsius

Laboratory Experiment No. 9 Corrosion of Metals

As a result of the cold working, the hardness follows a trend of increasing hardness. When the brass specimen was rolled its grains were elongated and therefore gave a higher hardness value. In relation to the percent reduction of the thickness, the hardness was slowly increasing. At 18% cold working there was already a significant amount of an increase of hardness. The jump was from about an initial 26 to about 78 hardness. At 50 % the hardness had increased all the way to roughly 91 Hardness as seen in figure 1. Once the Brass Specimen had been rolled to 50% thickness of its initial thickness, the specimen could now be heated at different temperatures to analyze its hardness. Once the brass specimens had been heated, they were quenched in water and tested for its hardness. It wasn’t until a temperature of 300 degrees Celsius that we saw a change in its hardness as shown in figure 2. As the temperature increased, there was decrease in hardness. This is since the grain structure it altered at higher temperatures. The grain size of the brass specimen had appeared to increase in size when they were heated at very high temperatures.

Laboratory Experiment No. 9 Corrosion of Metals In figure 3, the grain size in relation to the temperature is shown and it clearly shows an increase in grain size. The grain size is calculated in the section below named calculations. The grain size increases as the temperature is increased. In figures 4 – 9 the microstructures of the Brass specimens at 500, 600, 700 degrees Celsius are displayed. The microstructures also show the alteration of the grain size as the temperature is increased. In figure 4 the grain size is not as big compared to the grain size of the microstructure displayed in figure 9. In figures 4-9 it is visually apparent that the microstructure of the brass specimens were altered in the annealing process.

Calculations: Magnification=

Widthof Image Real widthof Specimen

of image height of image x( ( width ) magnification magnification )

True Area=

N=(Number of Grains)/(True Area) N=2G −1 500°C Brass Specimen

5.125∈ ¿ =20.5 .250 Magnification=¿ 5.125∈ ¿ 20.5 ¿ ¿ 4.125∈ ¿ 20.5 ¿ ¿ True Area=¿ 2

0.050305 ∈ ¿=2564.364 N =(129)¿

Laboratory Experiment No. 9 Corrosion of Metals G=1+

(

ln (2564.364 ) =12.32 µm ln ( 2 )

)

600°C Brass Specimen

0.050305 ∈2 ¿=1848.727 N=(93)¿ G=1+

(

)

ln (1848.727 ) =11.85 µm ln ( 2 )

700°C Brass Specimen

0.050305 ∈2 ¿=542.365 N=(93)¿ G=1+

(

)

ln (542.635 ) =10 µm ln ( 2 )

Conclusions: To conclude the experiment involved the measuring of hardness and rolling of a brass specimen to analyze the effect of cold work and annealing. The purpose of this experiment was to see how the hardness and strength are altered in different situations such as rolling the metal or heating up the metal. The experiment was able to confirm that grain sizes are increased in the annealing process. The results of the experiment displayed an increase of hardness as the thickness of the specimen was reduced. Temperature was also a factor as the temperature also showed defects to the material. The temperature decreased the hardness of the material as the ductility increased. The temperature effected the material because grain structures are altered in the annealing process. As a result of this experiment, a better insight on the process of cold working and annealing was demonstrated through the process. It was also discovered that there are many factors to consider when using materials and hardness is one of them. So being familiar with defects of a material are extremely useful as it is very important to considering on engineering applications.

Laboratory Experiment No. 9 Corrosion of Metals References: 1. Callister, W. D., & Rethwisch, D. G. (2013). Fundamentals of materials science and engineering: An integrated approach. New York: John Wiley & Sons. 2. Experiment 5 - Cold Work, Recovery, Recrystallization and Grain Growth. (n.d.). Retrieved from http://www.csun.edu/~bavarian/Courses/MSE%20227/Labs/5Cold_Working_Brass.pdf 3. Cold Work & Annealing Process. (n.d.). Retrieved November 09, 2020, from https://sites.google.com/site/coldworkannealingprocess/...