MAE 3324 CH11

Question 1

What are the three main fabrication techniques for metals?

Answer 1

Forming
Casting
Miscellaneous

Ref: Lecture slides

Question 2

Describe forming with respect to metal fabrication.

Answer 2

This refers to forging with simple tools such as hammers and presses after heating. Used by blacksmiths.

Ref: Lecture Slides

Question 3

Describe casting with respect to metal fabrication.

Answer 3

Motel metal is placed into a pre-fabricated mold where it cools.

Extra Notes: Telsa has the biggest casting machine in the world.

Ref: Lecture Slides

Question 4

Describe what fabrication options are available for metals outside of forming and casting.

Answer 4

Powder metallurgy, welding

Ref: Lecture Slides

Question 5

What are the two types of heat treatments?

Answer 5

Hot working
Cold working

Ref: Lecture Slides

Question 6

Describe “Hot Working.”

Answer 6

Hot-working process metals are plastically deformed above their recrystallization temperature. Being above the recrystallization temperature allows the material to recrystallize during deformation. This is important because recrystallization keeps the materials from strain hardening, which ultimately keeps the yield strength and hardness low and ductility high.

Ref: Wikipedia

Question 7

Describe “Cold Working.”

Answer 7

Cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Unlike hot working, cold working causes the crystal grains and inclusions to distort following the flow of the metal; which may cause work hardening and anisotropic material properties. Work hardening makes the metal harder, stiffer, and stronger, but less plastic and may cause cracks of the piece.

Ref: Wikipedia

Question 8

True or False

There are small deformations when using hot working.

Answer 8

False, large deformations occur.

Ref: Lecture Notes

Question 9

True or False

Cold working results in strain hardening.

Answer 9

True

Ref: Lecture Notes

Question 10

True or False

During cold working, small deformation are achieved below the recrystallization temperature.

Answer 10

True

Ref: Lecture Notes

Question 11

What is the difference between steel and cast iron?

Answer 11

Steel has less than 1.4% wt carbon while cast irons have between 3 to 4.5% wt carbon.

Ref: Lecture Notes

Question 12

What are the three main Copper alloys?

Answer 12

Brass, Bronze, and Cu-Be.

Question 13

What are the six main non-ferrous alloys?

Answer 13

1. Copper (Cu) Alloys
2. Titanium (Ti) Alloys
3. Noble Metals
4. Refractory Metals
5. Mg Alloys
6. Aluminum (Al) Alloys

Ref: Lecture Notes

Question 14

In brass, what is the substitutional impurity? What is brass commonly used for?

Answer 14

Zinc. Costume jewelry, and coins due to its corrosion resistance.

Ref: Lecture Notes

Question 15

What are the substitutional impurities in Bronze? What is bronze commonly used for?

Answer 15

Sn, Al, Si, and Ni
Bushing, landing gear, etc

Ref: Lecture Notes

Question 16

What are some benefits/downsides and uses for Titanium alloys?

Answer 16

Low density but reactive at high temperatures.
Lots of Aerospace applications

Ref: Lecture Notes

Question 17

True or False

Noble metals are oxid./corr. resistant.

Answer 17

True

Ref: Lecture Notes

Question 18

Refractors metals have ___ melting temperatures.

Answer 18

High

Ref: Lecture Notes

Question 19

Mg. Alloys have a comparatively ___ density but ____ easily.

Answer 19

low
ignites

Ref: Lecture Notes

Question 20

What are the substitutional impurities commonly used in Al alloys?

Answer 20

Cu, Mg, Si, Mn, Zn

Ref: Lecture Notes

Question 21

Cast Irons have a ___ melting point and are __ to cast.

Answer 21

Low
Easy

Ref: Lecture Notes

Question 22

True or False

Cast Iron is generally brittle.

Answer 22

True

Ref: Lecture Notes

Question 23

True or False

With respect to cast irons, Cementite will decompose to ferrite + graphite over a very long time.

Answer 23

True

Ref: Lecture Notes

Question 24

Give the characteristics of Gray Iron.

Answer 24

Graphite flakes
Weak and brittle in tension
Stronger in compression
Excelling vibrational dampeneing
Wear-resistant

Ref: Lecture Notes

Question 25

Give the characteristics of Ductile Iron as opposed to gray iron.

Answer 25

Gray Iron plus Mg and/or Ce
Graphite as noodles not flakes
Matrix is usually pearlite
Stronger but less ductile

Ref: Lecture Notes

Question 26

Give the characteristics of white iron.

Answer 26

<1 wt% Si
Pearlite + Cementite
Very hard and brittle

Ref: Lecture Notes

Question 27

Give the characteristics of Malleable Iron.

Answer 27

Heat treat at 800-900C
Graphite in rosettes
Generally strong and ductile

Ref: Lecture Notes

Question 28

Give the characteristics of compacted graphite iron.

Answer 28

Obtained by adding a small amount of Ce or Mg to Gray Cast Iron
Relatively high thermal conductivity
Good resistivity to thermal shock
Lower oxidation at elevated temperatures

Ref: Lecture Notes

Question 29

What are the five types of Annealing

Answer 29

1. stress relief
2. Process Anneal
3. Spheriodize
4. Full Anneal
5. Normalize

Ref: Lecture Notes

Question 30

What is the “hardenability of metals” concerned with?

Answer 30

It is a measure of the ability of a steel to be heat treated. Increases with alloy content.