What is the radius of the bcc and fcc gaps?
fcc: oct: 0,052 nm
tetra: 0,028 nm
bcc: oct: 0,019 nm
tetra: 0,036 nm
Where are the octaedrical and tetrahedral interstices located in the FCC structure?
Where are the octaedrical and tetrahedral interstices located in the BCC structure?
What type of distorrtion is the martensitic distortion?
tetragonal
Is the Martensite transformation athermal? Why?
Principally yes, but small amounts of Martensite can form isothermally
What are the morphologic types of martensite? How do they form?
What are the difference in morphology (and metallurgy) between plate and lathe martensite.
lath:
high density in dislocations
interlath residual austenite
parallel strucutures
plate:
high density in twinning
high amounts of retained austenite
What influence does the grain size have on the Martensite starting temperature?
From which attributes originates the hardness of Martensite?
presence of carbon in the material, which leads to the following effects:
distortion of the tetragonal cristal lattice
solution hardening
structural defects
What is the change in volume from the Martensite transformation?
0.0010 nm^3=4% elongation
What are the origins of quench cracks?
thermal contraction due to cooling and expansion of the unit cell work against eachother and can form very high internal stresses.
=> possible plastic deformation
What are the factors for the martensite strength?
austenite grain size
solute concentration
precipitation hardening (after tempering)
substructure (dislocations, twins…)
What is the purpose of the Norstrom equation?
To calculate the increase in yield strength for additional Carbon.
What is the effect of substitutional solute atoms on martensite strength?
Very little direct contribution
indirect influence through:
Ms temp
hardenability
amount of retained austenite
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