MAE 3324 CH11 Flashcards
What are the three main fabrication techniques for metals?
Forming
Casting
Miscellaneous
Ref: Lecture slides
Describe forming with respect to metal fabrication.
This refers to forging with simple tools such as hammers and presses after heating. Used by blacksmiths.
Ref: Lecture Slides
Describe casting with respect to metal fabrication.
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
Describe what fabrication options are available for metals outside of forming and casting.
Powder metallurgy, welding
Ref: Lecture Slides
What are the two types of heat treatments?
Hot working
Cold working
Ref: Lecture Slides
Describe “Hot Working.”
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
Describe “Cold Working.”
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
True or False
There are small deformations when using hot working.
False, large deformations occur.
Ref: Lecture Notes
True or False
Cold working results in strain hardening.
True
Ref: Lecture Notes
True or False
During cold working, small deformation are achieved below the recrystallization temperature.
True
Ref: Lecture Notes
What is the difference between steel and cast iron?
Steel has less than 1.4% wt carbon while cast irons have between 3 to 4.5% wt carbon.
Ref: Lecture Notes
What are the three main Copper alloys?
Brass, Bronze, and Cu-Be.
What are the six main non-ferrous alloys?
- Copper (Cu) Alloys
- Titanium (Ti) Alloys
- Noble Metals
- Refractory Metals
- Mg Alloys
- Aluminum (Al) Alloys
Ref: Lecture Notes
In brass, what is the substitutional impurity? What is brass commonly used for?
Zinc. Costume jewelry, and coins due to its corrosion resistance.
Ref: Lecture Notes
What are the substitutional impurities in Bronze? What is bronze commonly used for?
Sn, Al, Si, and Ni
Bushing, landing gear, etc
Ref: Lecture Notes
What are some benefits/downsides and uses for Titanium alloys?
Low density but reactive at high temperatures.
Lots of Aerospace applications
Ref: Lecture Notes
True or False
Noble metals are oxid./corr. resistant.
True
Ref: Lecture Notes
Refractors metals have ___ melting temperatures.
High
Ref: Lecture Notes
Mg. Alloys have a comparatively ___ density but ____ easily.
low
ignites
Ref: Lecture Notes
What are the substitutional impurities commonly used in Al alloys?
Cu, Mg, Si, Mn, Zn
Ref: Lecture Notes
Cast Irons have a ___ melting point and are __ to cast.
Low
Easy
Ref: Lecture Notes
True or False
Cast Iron is generally brittle.
True
Ref: Lecture Notes
True or False
With respect to cast irons, Cementite will decompose to ferrite + graphite over a very long time.
True
Ref: Lecture Notes
Give the characteristics of Gray Iron.
Graphite flakes Weak and brittle in tension Stronger in compression Excelling vibrational dampeneing Wear-resistant
Ref: Lecture Notes
Give the characteristics of Ductile Iron as opposed to gray iron.
Gray Iron plus Mg and/or Ce
Graphite as noodles not flakes
Matrix is usually pearlite
Stronger but less ductile
Ref: Lecture Notes
Give the characteristics of white iron.
<1 wt% Si
Pearlite + Cementite
Very hard and brittle
Ref: Lecture Notes
Give the characteristics of Malleable Iron.
Heat treat at 800-900C
Graphite in rosettes
Generally strong and ductile
Ref: Lecture Notes
Give the characteristics of compacted graphite iron.
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
What are the five types of Annealing
- stress relief
- Process Anneal
- Spheriodize
- Full Anneal
- Normalize
Ref: Lecture Notes
What is the “hardenability of metals” concerned with?
It is a measure of the ability of a steel to be heat treated. Increases with alloy content.
