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Chapter 3

Chapter 3 . Structure and manufacturing Properties of Metals. Crystal structure of metals Role of various imperfections Importance of grain Failure and fracture of metals Ferrous and non-ferrous metals, alloys. Covalent Bond. Some Common Features of Materials with Covalent Bonds: Hard

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Chapter 3

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  1. Chapter 3 Structure and manufacturing Properties of Metals • Crystal structure of metals • Role of various imperfections • Importance of grain • Failure and fracture of metals • Ferrous and non-ferrous metals, alloys

  2. Covalent Bond • Some Common Features of Materials with Covalent Bonds: • Hard • Good insulators • Transparent • Brittle or cleave rather than deform

  3. Metallic bond • Some Common Features of Materials with Metallic Bonds: • Good electrical and thermal conductors due to their free valence electrons • Opaque • Relatively ductile

  4. Ionic Bond • Some Common Features of Materials with Ionic Bonds: • Hard • Good insulators • Transparent • Brittle or cleave rather than deform

  5. Body-Centered Cubic (BCC) Structure Face Centered Cubic (FCC) Structure Hexagonal Close Packed (HPC) Structure

  6. the atoms in rows A and C are no longer aligned cubic lattice structures allow slippage to occur more easily than non-cubic lattices, so hcp metals are not as ductile as the fcc metals.

  7. Interstitial impurity atom • Edge dislocation • Self interstitial atom • Vacancy • Precipitate of impurity atoms • Vacancy type dislocation loop • Interstitial type dislocation loop • Substitutional impurity atom Defect

  8. a dislocation is a crystallographic defect, or irregularity, within a crystal structure Simple Cubic Lattice showing atomic planes (marked in red) Screw dislocation Edge dislocation Burgers vector in black, dislocation line in blue.

  9. Edge Dislocation Screw Dislocation

  10. Grain a) Nucleation of crystals b) crystal growth c) irregular grains form as crystals grow together d) grain boundaries as seen in a microscope

  11. Atoms along the boundary packed less efficiently Grain Boundary more disordered Polycrystalline Deformation before after

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