12-13 Flashcards
For a FeFe3C graph:
What does hypoeutectoid slow cooling produce from austenite?
Ferrite+Pearlite
For a FeFe3C graph:
What does a hypereutectoid slow cooling produce from austenite?
Cemetite+Pearlite
For a FeFe3C graph:
What does a slow cooling on the eutectic point produce from austenite?
Pearlite
What is Pearlite?
A finely laminated mixture of cementite and ferrite
What is spheroidite?
The end product of slow and moderate cooling.
Easy to reheat and shape into other materials.
Made of cementite and ferrite (pearlite).
What is the timeline of a slow cooling austenite compound?
What does it turn into when it is reheated?
Austenite —-> Ferrite + cementite (pearlite)
Reheated:
Spheroidite
What is the timeline of a moderate cooling austenite compound?
What does it turn into once it’s been reheated?
Austinite –> Bainite
Reheated (700º):
spheroidite
What is the timeline of a rapid cooling Austine compound?
Austinite –> martensite
Reheated (between 200-700º):
Tempered Martensite
What is martensite?
Formed by the rapid cooling of austenite, in which traps carbon causing it to be more brittle.
What is tempered martensite?
Much harder and stronger than martensite as it has more ferrite-cementite phase boundaries, this allows it to have dislocation motion.
What is upper bainite?
Made up of ferrite and cementite is precipitated between the ferrite plates.
Formed at higher temperatures than lower bainite.
The lines of cementite in the material as they are parallel.
Not as hard as lower bainite.
What is lower bainite?
Made up of ferrite and cementite that is precipitated between the ferrite plates.
Formed from lower temperatures than upper bainite.
Has more grade boundaries which makes it harder, as they will block the dislocation.
What is spheroidite?
Formed by the reheating (700º)of; ferrite+cementite (pearlite) and bainite.
Need to reheat for a long time to diffuse the carbon out.
Softest and most ductile type of steel.
What is course pearlite?
Made up of ferrite and cementite.
Weaker than fine pearlite, as the finer the layers the more resistance to slip. (still not very hard and quite ductile)
Made from the slow cooling of austenite.
What is fine pearlite?
Made up of ferrite and cementite.
Stronger than coarse pearlite, as the finer the layers the more resistance to flip. (still not very hard and quite ductile.
Made from the slow cooling of austenite.
From Hardest to most ductile what is the order for non-equilibrium transformation products?
Martensite, tempered martensite, lower bainite, upper bainite, fine pearlite, coarse pearlite and spheroidite.
How does weight percentage of carbon affect the hardness of the material?
directly proportional, increase with it.
How does the weight percentage of carbon affect the ductility of material?
Indirectly proportional decreases with it.
What is tempering?
The process of heating a metal below its melting point then cooling it in air, this increases it brittleness and increasing toughness.
What is quenching?
When you rapidly cooling a material (e.g in oil or water) in order to increase the hardness of a material.
What causes equilibrium products?
Slow cooling of austinite
What causes non-equilibrium products?
Moderate/fast cooling of austinite
What is an isothermal diagram look like?
Temperature against time, to show what can be produced during quenching and tempering
What is the temperature that pearlite become bainite on an isothermal diagram?
540º
Which pearlite and bainite are above the other on an IT diagram?
Coarse pearlite and upper bainite.
What is the difference between hypo and hyper eutectoidic isothermal diagrams?
Hypo will have ferrite
Hyper will have cementite
