Intro to material structures

Question 1

What is steel composed by?

Answer 1

Alloy of carbon (kol) and iron to make steel.

Question 2

Name the differenct structure levels of metals

Answer 2

Atomic level - form a crystal lattice
Nano level - lattice types and lattice defects
Micro level - grains, phases and defects
Macro and meso - up to the surface where we can see cracks and roughness

Question 3

Whta is the conswquence of the metallic bond in metals?

Answer 3

thermal and electrical conductivity, plastic deformation and ductility

Question 4

What does it mean when you say that “metals are a crystalline material”?

Answer 4

The meaning of that is that the atoms are arranged in a specific order in a grid called “crystal lattice”.

Can be FCC = face centered cube
or BCC = body centeres cube

Question 5

How does metals in short occur?

Answer 5

Metals are formed when you remove energy from the atoms since they will move less and less and the items will get closer and then when the temperature is below the melting point they will arise in a certain position.

Question 6

Name som defects sin the crystal lattice

Answer 6

• Point defect
  Defects a single point in the lattice
  Vacancy: an atom is missing
  Interstitial: an atom occupies a place
  Substitutional: one type of atom replaces another type
  Self-interstitial: presens of an extra atom of the same type, squeezes in
• Line defects
  Dislocations: a number of atoms are offset from their usual position in the lattice.
  Edge dislocation: an extra half plane of atoms in the lattice, making the atomic bond to break and deform in the way so the half plane of atoms glide through the lattice.
  Screw dislocation

Question 7

Which are the common reinforcing mechanisms in metallic materials?

Answer 7

1. Solid solution strengthening
2. Precipitation hardening
3. Reduction of grain size
4. Strain or work hardening

Question 8

Describe solid solution hardening

Answer 8

An element with smaller or larger atoms is mixed into the metal. This disrupts the perfect arrangement of atoms in the metal, and the precense of the new atoms makes it harder for dislocations in the base metal.

Question 9

Describe precipitation hardening

Answer 9

The thing is to change solubiilty with temperature to produce fine particles and provide dislocations. Heating over the solvent temp and is then soaked. Then you do quenching (rapid cooling) and last aging.

Question 10

Describe Reduction of grain size

Answer 10

The smaller the grains, the higher yeild strength. Small grains are great for high yeild, high stress etc.

Question 11

Strain or work hardening

Answer 11

Strain hardening, also known as work hardening, is a phenomenon where a metal or polymer becomes stronger and harder as it undergoes plastic deformation