Metal alloys and phase diagrams

Question 1

What is an alloy?

Answer 1

a combination of different materials to metals to improve the material properties of the metal

Question 2

What are the components of an alloy?

Answer 2

the elements which make up the alloyed metal

Question 3

What is a phase?

Answer 3

a material with the same:
- structure and atomic arrangment
- composition and properties
throughout
and has a definitive interface with adjacent phases

Question 4

What is a solution?

Answer 4

a combination of phases where on phase is meixed at an atomic level with aonther

Question 5

what is a compound?

Answer 5

a combination of phases where the components are chemically bonded to each other

Question 6

Describe a substitutional solid solution

Answer 6

the solute element replaces solvent atoms in the lattice structure

Question 7

What are the Hume-Rothery’s Conditions for unlimited solubility

Answer 7

1. Similar sized atoms (less than 15% difference in
   radius)
2. Same crystal structure
3. Same number of electrons available for bonding
   (valence)
4. Similar tendency to attract electrons (electronegativity)

Question 8

What is Solid Solution Strengthening?

Answer 8

substituted solute with different size to the sulvent atoms prevent dislocations moving through the material thus reducing ductility and increasing yeild strength and hardness

Question 9

Describe and Interstitial solid solution

Answer 9

When solute atoms are much smaller than solvent atoms the solute atoms
can take up positions in gaps between solvent atoms

Question 10

What is the Alloy constitution of an alloy?

Answer 10

a description of the componds and phases that are present in the alloy

Question 11

What is Phase structure?

Answer 11

describes how phases are arranged and the alloy constitution

Question 12

What is a phase diagram

Answer 12

a graph of temperature against percentages mass of solute present.
each phase is labelled and divided from each other

Question 13

What is a tie line

Answer 13

a horizontal line
drawn through the point
on the phase diagram
representing the alloy of
interest.
extending the line to the boundaries tells the percentage of the solute in each phase

Question 14

Describe the lever rule

Answer 14

cauculates the proportion of each phase present
𝑃1 =(𝑋_2−𝑋)/(𝑋_2−𝑋_1)
or
𝑃2 =(𝑋−𝑋_1)/(𝑋_2−𝑋_1)
where P is the amount of phase X is the composition of the alloy and X_1 , X_2 are the composition of the phases

Question 15

Describe the lever rule geometrically

Answer 15

the length of the tie line between the alloy composition and the opposite phase boundary
divided by the length of the tie line