the science of engineering materials
mond.araba
cpt8hwsp15.docx
MEE 312 Spring 2015 Chapter 8:
1. Fill in the table below as it relates to annealing:
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Stage |
Recovery |
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Change in microstructure |
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New grains nucleate |
Grains Grow |
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Change in properties |
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Further reduction in strength, further increase in ductility |
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Temperature |
Below Trc |
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· Trc |
2. Fill in the following chart using the following symbols (+ means goes up significantly, - means goes down significantly, = means stays pretty much the same). The material has a melting temperature of 2500 C, and a stress relief anneal could be done at about 500- 600 C and grain growth occurs at 1000 C.
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Annealing Temp (C) |
Electrical Conductivity (ohm -1*cm-1) |
Yield Strength (MPa) |
Grain Size (mm) |
Stage of Annealing |
Microstructure changes |
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400 |
Baseline |
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600 |
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800 |
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1000 |
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1200 |
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Mechanical Properties |
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Hardness, Brinell |
47 |
47 |
AA; Typical; 500 g load; 10 mm ball |
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Ultimate Tensile Strength |
27000 psi |
AA; Typical |
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Tensile Yield Strength |
11000 psi |
AA; Typical |
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Elongation at Break |
20 % |
AA; Typical; 1/16 in. (1.6 mm) Thickness |
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Elongation at Break |
22 % |
AA; Typical; 1/2 in. (12.7 mm) Diameter |
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Modulus of Elasticity |
10600 ksi |
AA; Typical; Average of tension and compression. Compression modulus is about 2% greater than tensile modulus. |
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Ultimate Bearing Strength |
50000 psi |
Edge distance/pin diameter = 2.0 |
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Bearing Yield Strength |
19000 psi |
Edge distance/pin diameter = 2.0 |
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Poisson's Ratio |
0.33 |
0.33 |
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Fatigue Strength |
13000 psi |
AA; 500,000,000 cycles completely reversed stress; RR Moore machine/specimen |
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Machinability |
30 % |
0-100 Scale of Aluminum Alloys |
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Shear Modulus |
4060 ksi |
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Shear Strength |
18000 psi |
AA; Typical |
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Electrical Properties |
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Electrical Resistivity |
3.49e-006 ohm-cm |
AA; Typical at 68°F |
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Thermal Properties |
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CTE, linear 68°F |
12.9 µin/in-°F |
AA; Typical; Average over 68-212°F range. |
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CTE, linear 250°C |
13.7 µin/in-°F |
Average over the range 20-300ºC |
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Specific Heat Capacity |
0.209 BTU/lb-°F |
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Thermal Conductivity |
1340 BTU-in/hr-ft²-°F |
AA; Typical at 77°F |
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Melting Point |
502 - 638 °C |
935 - 1180 °F |
AA; Typical range based on typical composition for wrought products 1/4 inch thickness or greater. Eutectic melting is not eliminated by homogenization. |
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Solidus |
935 °F |
AA; Typical |
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Liquidus |
1180 °F |
AA; Typical |
regarding this information. MatWeb data and tools provided by MatWeb, LLC.
Assume that you then cold work this material approximately 50%. On the same stress-strain curve, using a dashed line, please construct the stress strain curve for the AA 2024 material that had been subjected to the 50% cold work. Explain the following:
a. Why did you estimate the modulus to be as you drew it?
b. Would you estimate the hardness to be higher or lower for the cold worked material and why?
c. Would you expect the % elongation to be higher or lower for the cold worked material and why?
