http://www.mse.ncsu.edu/zhu Materials Science & Engineering

•Objectives/outcomes: You will learn the following:

•Plastic deformation single crystals.

•The slip mechanism and dislocations.

•Slip systems and the critical resolved shear stress.

•Schmid’s law. •Twinning

•Grain boundary strengthening

MSE200 Lecture 8 (CH. 6.5-6.8)

Mechanical Properties I Instructor: Yuntian Zhu

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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http://www.mse.ncsu.edu/zhu Materials Science & Engineering

http://video.google.com/videosearch?q=dislocation+slip&hl=en&emb=0&aq=f#

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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Close packed

plane

Non-close-packed

plane

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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http://www.mse.ncsu.edu/zhu Materials Science & Engineering

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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r = Cos Cos

1A

Fr

r=

Slip

direction

Normal to

Slip plane

0A

F=

A1=Area of

Slip plane

F

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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FCC metal

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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Stress-strain curve of single

and polycrystalline copper

Slip bands in polycrystalline

aluminum grains

Dislocations piled up

against grain boundaries

in stainless steel

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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Strain Hardening

Stress-Strain curves of 1018 steel

1018-Cold Rolled

1018-Annealed

http://video.google.com/videosearch?q=rolling&hl=en&emb=0&aq=f#emb=0&hl=en&q=cold+rolling&view=3

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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http://www.mse.ncsu.edu/zhu Materials Science & Engineering

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3 important strategies for increasing the strength:

http://www.youtube.com/watch?v=QVJ1DOIDl2A

http://www.mse.ncsu.edu/zhu Materials Science & Engineering

Example Problems: 6.9, 6.10

Regular Problems, Download from web

Reading assignment: section 7.1-7.2