FINAL CHEAT SHEET - Chapter 2-Atomic Structure and...

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Chapter 2-Atomic Structure and Interatomic Bonding Ionic Bonds-electron transfer, nondirectional, hard/brittle, coulombic Covalent Bonds-electrons shared, bond directional Metallic Bonds-electrons delocalized, “electron cloud”, weakest of 3 Chapter 3-The Structure of Crystalline Solids Crystal Solids-Metals APF = n(4/3)πR 3 FCC BCC SC a 3 n 4 2 1 ρ = n x A N=N A ρ/A a 2R(2) 1/2 4R/(3) 1/2 R V c x N A CN 12 8 12 Closed Packed-FCC, HCP Polymorphism-materials can have more than 1 crystal structure Allotropy-Elemental (1-element) material that’s polymorphic Noncrystalline-lack systematic and regular atom arrangement Amorphous-Without form Chapter 4-Imperfections in Solids Point Defects: Vacancy-missing, Interstitial-extra For metals, interstitials << vacancies Self-interstitial-same atom wrong spot Impurities -Alloying-intentional addition of impurities -Solvent-species in greatest amount -Solute-species in minor amount Solid Solution-substitutional, interstitial -Decide whether substitutional -Size of atoms (similar), crystal structure, same valence/electroneg Dislocations: Edge-perp dislocation line/burger’s vector Screw-// to dislocation line/burger’s vector N v = Nexp(-Q/KT); find N by using density in ch2 Chapter 5-Diffusion -Material transport by atomic motion Vacancy-move into adjacent sites; Interstitial-move into interstitial sites Interstitial-small atoms b/c sites are small Rate Interstitial >> Rate Vacancy (Small atoms more mobile) Steady State-diffusion flux does not change with time Fick’s 1 st Law: J = -D(dC/dx); J-diffusion flux, D-diff coeff, conc grad Nonsteady State Diffusion: Fick’s 2 nd Law: C x -C 0 = 1 – erf x . x 2 /Dt =const C s -C 0 2 (DT) 1/2 Factors: Size of diff species, size host, defect, temperature Diff Coeff varies exponentially with temp: D = D 0 exp(-Q/RT) Chapter 6-Mechanical Properties of Metals Engineering Stress: σ = F/A; Engineering Strain: Є = (L i -L 0 )/L 0 σ = EЄ; Hook’s law is true when deformation is elastic E ceramic > E metals > E polymer ; Higher Temp lower E b/c weaker bonds Poisson’s Ratio: υ = -Є x z , x is area z is length Plastic deformation deformed past elastic permanent broken bonds Yield Strength-stress until plastic deformation; Tensile: Max Stress Ductility: plastic deformation before fracture Resilience: Energy until plastic deformation; Toughness: Energy to fracture U r = (½)σ y Є y = σ 2 y /2E Hardness: Resistance to localized plastic deformation σ y = σ (1+Є); Є T = ln(1+Є) Design/Safety Factor: σ w = σ y /N Chapter 7-Dislocation and Strengthening Mechanisms Plastic deformation is a result of motion of dislocations Slip easy-high ductility; slip hard-low ductility Slip plane/directions-planes/directions with densest atomic packing Grain size reduction-boundaries act as barriers to dislocation movement -Undesirable at higher temperatures due to creep and sliding of boundaries - σ y = σ 0 + k y d -1/2 Solid-Solution Strengthening -Alloy metals form a substitutional or interstitial solid solution
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  • Spring '08
  • Lan
  • Tensile strength, Interatomic Bonding Ionic, Ceramics Ceramics, Applications and Processing of Polymers, Structures Polymers

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FINAL CHEAT SHEET - Chapter 2-Atomic Structure and...

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