YouTube: SEM study of slip in deformed cadmium single crystalSEM study of slip in deformed cadmium single crystal Reduced Strength due to Dislocations: YouTube: Model of slip by the movement of an edge dislocation Dislocation processes in precipitation-hardened metals during in situ deformation in an HVEMModel of slip by the movement of an edge dislocation Dislocation processes in precipitation-hardened metals during in situ deformation in an HVEM YouTube: 3D atom dislocation3D atom dislocation Predicted by Theory: YouTube: Slip by movement of whole lattice planesSlip by movement of whole lattice planes YouTube: Aluminum Tensile Test.Aluminum Tensile Test. YouTube: Dislocation motion along grain boundary.avi YouTube: Dislocations in motionDislocation motion along grain boundary.aviDislocations in motion Save until defects: YouTube: “Brass Tension Test”“Brass Tension Test”

Materials Moments: Tareq/Hisham—Creating new polymer composites Ryan/Jesse—Footballs

Uniform vs. Non-uniform plastic deformation

fig_06_11 Engineering Stress-strain curve for typical metals

YouTube YouTube: Aluminum Tensile Test.Aluminum Tensile Test. Stress-strain curve shown

Question of the Day: How does Ductility relate to Plastic Deformation?

Ductility % plastic strain at fracture (after subtracting off elastic recovery)

Toughness The effect of aging on crack-growth resistance and toughening mechanisms in human dentin

Hardness Resistance to scratching, denting

Brittle Deformation

Brittle Deformation Brittle—Little or no plastic deformation before failure New Steel Pressure Vessel Failed during Hydraulic Test Improper heat Treatment after Welding (PWHT)

Brittle Materials Very little plastic deformation before failure Fracture strains <5%

Brittle Deformation Cast Aluminum Motorcycle Engine Cover

Cast Iron Cast Aluminum Ultra High-C Steel Brittle Metals

Brittle Materials mild steel: 0.16–0.29 wt% C Cast Iron: wt% C (ductile) (brittle)

Brittle Failure: Tensile test of Nodular Graphite Cast Iron

Engineering Stress-Strain for metals

Deformation on the atomic scale Elastic Plastic Brittle

Mechanical Property terms Elastic - Elasticity Plastic - Plasticity Stiff - Stiffness Ductile - Ductility Strong - Strength Brittle - Brittleness Tough - Toughness Hard - Hardness

Chapter 7 Section 7.1–7.4 Dislocations Slip Systems

Plastic deformation is due to atomic-level Shear stresses

How do we generate shear stresses when a sample is in a tensile test? Plastic Deformation

f07_07_pg182 Max. shear stress is on a plane 45º from the tensile stress

f08_07_pg182 Fig. 7.8 Single xl after plastic deformation due to tensile stress Before deformation

Shear Stress required for plastic deformation in single Cu crystal (Based on atomic bonding strengths)  theoretical ≈ 1000 Mpa  true < 100 MPa (  = shear stress)

Predicted by Theory: YouTube: Slip by movement of whole lattice planes Slip by movement of whole lattice planes

Line defects edge dislocation, screw dislocation

YouTube: “Brass Tension Test”“Brass Tension Test” Plastic Deformation YouTube: 3D atom dislocation3D atom dislocation YouTube: Model of slip by the movement of an edge dislocationModel of slip by the movement of an edge dislocation

Real Dislocations: Dislocation processes in precipitation-hardened metals during in situ deformation in an HVEM YouTube: Dislocation motion along grain boundary.avi YouTube: Dislocations in motion YouTube: Copy of particle disl inter high t.avi Dislocation processes in precipitation-hardened metals during in situ deformation in an HVEMDislocation motion along grain boundary.aviDislocations in motion Copy of particle disl inter high t.avi

SEM {100} planes SEM single crystal of cadmium deforming by dislocation slip on {100} planes.

f09_07_pg183 Fig. 7.9 Slip in a single zinc crystal YouTube: SEM study of slip in deformed cadmium single crystalSEM study of slip in deformed cadmium single crystal

Slip Systems: { x y z }

Fig. 7.6 Slip Systems

Table 7.1

( ) ( ) ( ) ( ) ( ) ( )

Plastic Deformation Section 7.5: Single Crystals

f07_07_pg182 Max. shear stress is on a plane 45º from the tensile stress

f08_07_pg182 Slip in a single crystal Fig. 7.8

Table 7.1

Dislocation Densities Range: 10 3 mm mm -2 Carefully solidified Metals Highly deformed Metals

When it comes to Plastic Deformation… Dislocations Rule!

Plastic Deformation Section 7.6: Polycrystalline Materials

f10_07_pg186 Plastic Deformation: Slip in Polycrystalline Copper Fig. 7.1 (173x photomicrograph)

f11_07_pg186 Plastic Deformation: Polycrystalline Cold-worked Nickel Before deformationAfter deformation Fig x photomicrograph