Metals

Question 1

What are the two classifications of metal alloys

Answer 1

Ferrous

Nonferrous

Question 2

Describe Copper

Answer 2

Nonferrous
Soft, ductile
Hard to machine
Resists corrosion and highly conductive

Question 3

What are the two main copper alloys

Answer 3

Brass

Bronze

Question 4

Describe Brass

Answer 4

Cu + Zn
alpha brass has less than 35%Zn, FCC, soft
formed by cold working
alpha+beta brass has more than 35%Zn, BCC, strong
formed by hot working

Question 5

Describe Bronze

Answer 5

Cu + not Zn, so Sn, Al, Si, or Ni
stronger than brass
high corrosion resistance
used when tensile properties are needed

Question 6

Describe Aluminum

Answer 6

low density, high ductility
conductive and corrosion resistant
can be improved by alloying and cold work

Question 7

Describe Magnesium

Answer 7

lowest structural density
cannot be cold worked b/c HCP
good corrosion and oxidation resistance except in water
used for aircraft, missiles, cars

Question 8

Describe Titanium

Answer 8

low density, high melting point
very expensive because highly reactive at high temp
high strength, easily machined
good corrosion resistance at room temp
used for biomed

Question 9

Describe refractory materials

Answer 9

extremely high melting temp
ex) tungsten, niobium, tantalum
melting points in 2000-3000 C
strong interatomic bonds give high melting temp, strength

Question 10

Describe superalloys

Answer 10

high strength and corrosion resistance at high temps
alloys of Co, Ni, Fe, and refratory materials
used in aircraft and nuclear

Question 11

Describe noble metals

Answer 11

8, all the gem-like one, silver, gold, platinum

expensive, soft, oxidation resistant

Question 12

What is the principle component of ferrous alloys? Why are they popular?

Answer 12

Iron, Fe
Abundant
Cheap
Wide range of properties

Question 13

What are the three forms of pure iron?

Answer 13

alpha (ferrite) - BCC - max 0.022wt% C - soft and magnetic
gamma (austenite) - FCC - max 2.14wt% C - non magnetic
delta (ferrite) - BCC - unstable at low temps, useless

Question 14

What is the precipitate formed when the solubility limit of Carbon in Iron is surpassed?

Answer 14

Cementite, Fe3C

Question 15

What is the difference between steel and cast iron

Answer 15

steel : 0-2.14wt% C

cast iron : 2.14 - 6.7wt% C

Question 16

What are the three classifications of steels?

Answer 16

Eutectoid Steel : 0.76wt% C
Hypo-eutectoid steel : <0.76wt% C
Hyper-eutectoid steel: >0.76wt% C

Question 17

What is pearlite? When is it formed?

Answer 17

Alternating layers of ferrite and cementite, equilibrium cooling of steel

Question 18

What is bainite?

Answer 18

Very fine ferrite-cementite ‘needles’, formed during rapid cooling

Question 19

What is spherodite

Answer 19

Created when pearlite or bainite is held at pre-eutectoid temps for long time, all the cementite particles turn into spheres
Soft and weak

Question 20

What is martensite

Answer 20

formed when austenite is quenched
forms one solid state of BCT, or body centered tetragonal
strongest and hardest steel

Question 21

Describe stainless steel

Answer 21

At least 11wt% Cr
corrosion resistant
high temp oxidation resistant

Question 22

Describe cast irons

Answer 22

brittle, must be cast, not worked

Question 23

What are the disadvantages of ferrous alloys

Answer 23

Heavy
Low conductivity
Often corrode