2007-MECH141-07%20dislocation%20_%20strenghtening.pdf(hit)___2007-MECH141-07%2Bdislocation%2B%2526%2

2007-MECH141-07%20dislocation%20_%20strenghtening.pdf(hit)___2007-MECH141-07%2Bdislocation%2B%2526%2

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Unformatted text preview: Dislocations & Strengthening Mechanisms - Chapter VII Dislocations & Strengthening Mechanisms - Chapter VII Atomic bond breaks Plastic deformation results from slip between atomic planes of crystals Deformation of zine single crystal Dislocations & Strengthening Mechanisms - Chapter VII Slip of crystal are from dislocation motion Dislocations & Strengthening Mechanisms - Chapter VII Why the strength of metals is much lower than the value predicted from the metallic bond? For example, the theoretical shear strength is well over 1000MPa actual shear strength of Cu is at least an Order of magnitude less than this. OR You can this way: Atomic bond breaks Why dislocation motion? Less force is required to move a dislocation!! Dislocations & Strengthening Mechanisms - Chapter VII Slip and Slip Plane The process by which a dislocation moves and causes a material to deform is called slip . The crystallographic plane along which the dislocation line traverses is the slip plane . Shear stress Dislocation motion Dislocations & Strengthening Mechanisms - Chapter VII The motion of an edge dislocation: The motion of a screw dislocation: The dislocation line motion is perpendicular to the stress direction The dislocation line motion is parallel to the direction of the applied shear stress. Dislocations & Strengthening Mechanisms - Chapter VII Slip System The combination of slip direction and slip plane is the slip system . Dislocations & Strengthening Mechanisms - Chapter VII An FCC unit cell and its slip system {111} type planes (4 planes) have all atoms closely packed. Slip occurs along <110> type directions ( A-B,A-C,D-E ) within the {111} planes. FCC has 12 slip systems - 4 {111} planes and each has 3 <110> directions Dislocations & Strengthening Mechanisms - Chapter VII * Generally, the metals having larger number of slip systems are more ductile than the one has smaller number of slip system. Thus, FCC & BCC metals are generally ductile and HCP is brittle.and HCP is brittle....
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This note was uploaded on 10/25/2011 for the course HUMA 002 taught by Professor Yu during the Spring '11 term at Alcorn State.

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2007-MECH141-07%20dislocation%20_%20strenghtening.pdf(hit)___2007-MECH141-07%2Bdislocation%2B%2526%2

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