Crystals and microstructures

Question 1

what are 3 different types of metal structure

Answer 1

• face centred cubic (FCC)
• body centred cubic (BCC)
• hexagonal close packed

Question 2

what is the trend for ductility in the 3 types of metal structure?

Answer 2

FCC>BCC>HCP

Question 3

What is the trend for strength in the three types of metal structure?

Answer 3

HCP>BCC>FCC

Question 4

define atomic packing factor

Answer 4

• the ratio between the volume of the basic atoms of the unit cell to the volume of the unit cell itself

Question 5

what is the equation for atomic packing factor?

Answer 5

APF = Volume of atoms in a unit cell (Vs) /
Total unit cell volume (Vc)

Question 6

what is the equation for the Vc for face centred cubic metal structures?

Answer 6

16R^3√2

Question 7

what is the equation for body centred cubic metals Vc?

Answer 7

(4/(root)3 x R)^3

Question 8

what determines density?

Answer 8

• mostly dependent on atomic weight

Question 9

what makes metals dense and polymers have low densities

Answer 9

• metals have heavy atoms
• polymers have light atoms

Question 10

what is the equation for theoretical density?

Answer 10

𝜌=𝑛𝐴/𝑉𝑐𝑁a
𝑛 = number of atoms associated with each unit cell
𝐴 = Atomic weight
𝑉𝑐 = Volume of unit cell
Na = Avogadro’s number (6.022 x 1023 atoms/mol)

Question 11

what are separate crystals in a polycrystalline structure called?

Answer 11

• a grain

Question 12

what are grain boundaries?

Answer 12

• things that separate the crystals

Question 13

what is extrusion?

Answer 13

• a process that elongates the grain structure