Iron carbide phase diagram Flashcards
What non-metal compound can be eutectics?
Ceramics and polymers; ceramics concerned with volcanoes - liquid magma cools to solid solutions
What percentages of C within Fe make steel?
~0-2.2% C
What percentages of C within Fe make cast iron?
~2.2-6.7%
What are the four phases of the Fe-Fe3C diagram?
alpha-ferrite; gamma-austenite; delta-ferrite; cementite
What are structural properties of alpha-ferrite?
Body centre cubic; solid solution of C in Fe; ductile and not very strong due to low C content
What are structural properties of austenite?
Face centre cubic; has more atoms due to atomic structure = larger lattice = can dissolve more C
What are structural properties of delta-ferrite?
Body centre cubic; only small C can dissolve
What are structural properties of cementite?
6.67% C; brittle and very strong
Why is there an absence of a beta phase in the Fe-Fe3C diagram?
Used to be one when it was observed that above the Curie point, there were magnetic properties present in the alloy and below there wasn’t = assumed there was a change in microstructure
What occurs at a eutectic point?
L –> S1 + S2
What occurs at a eutectoid point?
S1 –> S2 + S3
What occurs at peritectic point?
S1 + L –> S2
What occurs at the eutectoid point of the Fe-Fe3C diagram?
Austenite –> pearlite (alpha-ferrite + Fe3C); is not a homogenous structure, so has intermediate properties of the two phases; dark Fe3C plates, light ferrite plates
What is the microstucture of a hypoeutectoid alloy of the Fe-Fe3C diagram?
Solid solution of proeutectoid alpha-ferrite in pearlite; typical RTP steel
What is the microstucture of a hypereutectoid alloy of the Fe-Fe3C diagram?
Solid solution of proeutectoid cementite in pearlite
