Section 3C Strengthening

Section 3C Strengthening - Section 3 DISLOCATIONS and...

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MATE 210 Section 3 DISLOCATIONS and STRENGTHENING MECHANISMS What happens microstructurally during plastic deformation? How can we control the mechanical properties of materials? Stiffness (E), Strength ( ε %) (Smith Chapter 6.7- 6.8)
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MATE 210 Review of Dislocations Dislocations : localized crystal lattice distortion • seen by TEM (only high magnifications) • strain (distortion) in lattice • allow deformation with lower stress • movement ( slip ) results in plastic deformation (or net flow of atoms) grossly exaggerated picture (think on atomic scale):
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MATE 210 Dislocations move in response to stress: • interatomic bonds ruptured and reformed (like caterpillar movement) • net movement of large number of atoms can occur plastic deformation results! Dislocation Movement
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MATE 210 Slip systems FCC {111} close packed plane Along which direction (AA or BB ) will atoms move easier? Dislocations move along preferred direction in preferred planes !
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MATE 210 Slip Systems Dislocations move on preferred crystallographic planes and directions most dense atomic packed plane and direction (for minimum atomic distortion of dislocation motion) FCC: {111} <110> (12 slip systems ductile) BCC: {110} <111>, others some operable only at high temps HCP: {0001} <1120> (3 slip systems stiff)
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This note was uploaded on 04/02/2008 for the course MATE 210 taught by Professor Niebuhr during the Spring '05 term at Cal Poly.

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Section 3C Strengthening - Section 3 DISLOCATIONS and...

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