Dental Alloys

Question 1

What is a solid solution?

Answer 1

• metals that are soluble in each other, in solid state
  -> solvent: metal whose space lattice persists
  -> solute: other metal that enters space lattice
• metals are in one phase
  -> grains of alloys are homogenous => resemble pure metal
  -> not mechanically separable

Question 2

What are the 2 types of solid solutions?

Answer 2

1. Interstitial solid solutions
   - solute< solvent atom diameter
2. Substitutional solid solutions
   - similar solute & solvent atom diameter
   - random substitution

Question 3

What is a superlattice?

Answer 3

ordered substitution in a solid solution

• atoms of one metal occupy specific positions in space lattice of other metal
• fixed composition
• e.g. 50.2% gold, 49.8% copper alloy
  
  • Au atoms at corner, Cu atoms on faces of cube unit
  • form face centered cubic (FCC) lattice

Question 4

What are the factors determining the extend of solid solubility of 2 metals?

Answer 4

1. Atomic size of atoms
- differ<15% => favourable size factor for SS
- differ>15% => multiple phases upon solidification
2. Valency
- same valency => more likely to form SS
3. Chemical affinity
- high degree of affinity => form intermetallic compound instead
4. Lattice type
- metals w same type of lattice => form SS
- most metals in FCC (face centered cubic) => can form continuous series of SS

Question 5

Amount of each element is measured more frequently in __%

Answer 5

More frequently measured in wt% than in a%

(Weight, atomic)

Question 6

What is a Eutectic alloy?

Answer 6

• complete liquid solubility, limited solid solubility/complete solid insolubility

Question 7

Name the 3 kinds of alloy types.

Answer 7

1. Solid solutions
2. Eutectic alloys
3. Intermetallic compounds

Question 8

What are intermetallic compounds?

Answer 8

• atoms of 2 or more metals combined in a fixed ratio=> produce crystal different in structure from the individual metals
• forms when strong attraction present btw component atoms (e.g. copper-zinc, silver-tin)