MSE

• Critical resolved shear stress (CRSS)


  The maximum stress needed to deform a material
• Directions edge dislocation can move in response to applied shear stress

  • Random
  • Perpendicular to shear stress
  • Neither perpendicular nor parallel to shear stress
  • Parallel to shear stress
• Directions screw dislocation can move in response to applied shear stress

  • Random
  • Perpendicular to shear stress
  • Neither perpendicular nor parallel to shear stress
  • Parallel to shear stress
• Directions mixed dislocation can move in response to applied shear stress

  • Neither perpendicular nor parallel to shear stress
  • Random
  • Parallel to shear stress
  • Perpendicular to shear stress
• Cold working


  Mainly affects the material's external shape, but also changes the material's microstructure
• Polycrystalline material


  • Generally stronger than its single crystal counterpart because multiple crystals mean more individual crystals to resist stress
  • Because τr is smaller in polycrystalline material than in single crystals
  • Because slip in one crystalline must continue to adjacent crystallites for the material to yield
• How impurity atoms strengthen a material

  Impurity atoms hinder the movement of dislocations by acting as pinning joints
• Slip system


  The specific crystallographic plane and direction that atoms move in a crystal lattice
• Cold working techniques


  • Forging
  • Rolling
  • Extrusion
• Annealing


  Heat treatment process that reduces excessive hardness and increases toughness
• Strengthening techniques


  • Cold working
  • Grain size reduction
  • Alloying
• Effect of cold working on a material

  The material becomes brittle
• Effect of quenching on metal microstructure

  It affects the grain size by arresting grain growth
• Strain hardening


  The material becomes stronger and tougher when deformed
• Hall-Petch Equation


  States that the yield strength of a material is a function of the reciprocal of the sqrt of the average grain diameter
• Resolved shear stress


  Shear force divided by the area
• How dislocation movement contributes to material deformation

  By promoting slip
• Effect of strain hardening on dislocation density

  Increases dislocation density
• Benefits of annealing


  • Removing residual stresses
  • Restoring ductility
  • Enhancing the materials machinability
• Effect of grain size reduction on strength

  Increases strength
• Yield point


  The point at which the amount of applied stress causes the most favorably-oriented slip system to slip
• Relationship between angle of applied force and resolved shear stress

  They are directly proportional
• Extrusion


  A cold working process wherein a billet(workpiece) is forced through a forming die
• Martensite


  A very hard structure in steel produced by quenching steel very quickly
• Grain growth


  Is a function of both time and temperature
• Effect of large number of slip systems

  Makes a material ductile
• Concrete


  A composite material
• Ferrous alloy


  An alloy where the main element is iron
• Composite material


  A material made from 2 or more constituent elements with significantly different physical or chemical properties
• Vulcanization


  A process that increases rubber's hardness by mixing natural rubber with sulphur
• Whiteware ceramics


  The type of ceramic used in lavatories
• Brass


  A copper alloy composed of copper and zinc
• Copper


  The metal with the highest conductivity
• Carbon fiber


  High tensile strength carbon thread embedded in a polymer matrix
• Strain hardening


  Also known as work hardening
• Ceramic materials


  • Characteristic of high thermal resistance
• Refractory materials


  Chemically stable at high temperatures
• Strain recovery


  Brought about by recrystallization
• Thermosetting materials


  Maintain their shape once formed
• Dislocation annihilation


  The movement of dislocation towards each other until they cancel out