HW #12. TTT Diagrams & Phase
Diagrams
Given the TTT diagram for the solidification of a ceramic melt shown here, at which
temperature (isotherm) would crystallization occur FASTEST? - answer The C isotherm
- Middle line
- Cuts straight through and reaches the crystalline curve at the earliest time
Which of these cooling curves would give a microstructure that includes at least some
martensite phase? - answer A, B, and E only.
- These are the only curves that do not reach 100% of a Pearlite or Bainite phase
As you cool below a phase transformation temperature, the transformation rates for
both nucleation and growth initially increase with decreasing temperature because... -
answer...the absolute difference in free energy between parent and product phases
increases.
Which cooling curve would give a 100% Pearlite microstructure? (Assume once Pearlite
is formed it will NOT transform into Bainite.) - answerCurve C
- Crosses the 100% border and quenches from there
In this unary phase diagram, which point(s) violate(s) the Gibbs phase rule? -
answerPoint C
- At point C, 4 phases are in equilibrium: Solid1, Solid2, Solid3, and Solid4.
True/False: On a standard temperature-pressure UNARY phase diagram, it is possible
to have AREAS of the phase diagram that include 2 phases in equilibrium with one
another. - answerFalse
- This is unary, not binary
Shown below is the pressure vs. temperature unary phase diagram for SiO2. How many
solid polymorphs of SiO2 are shown in this phase diagram? - answer6 polymorphs
Use the the unary phase diagram for SiO2 shown here to solve this question. Assume
the system is in the Coesite phase at 2500 °C and 7 GPa of pressure (as labelled in the
image). Starting from these conditions, which of the following processes would melt the
Diagrams
Given the TTT diagram for the solidification of a ceramic melt shown here, at which
temperature (isotherm) would crystallization occur FASTEST? - answer The C isotherm
- Middle line
- Cuts straight through and reaches the crystalline curve at the earliest time
Which of these cooling curves would give a microstructure that includes at least some
martensite phase? - answer A, B, and E only.
- These are the only curves that do not reach 100% of a Pearlite or Bainite phase
As you cool below a phase transformation temperature, the transformation rates for
both nucleation and growth initially increase with decreasing temperature because... -
answer...the absolute difference in free energy between parent and product phases
increases.
Which cooling curve would give a 100% Pearlite microstructure? (Assume once Pearlite
is formed it will NOT transform into Bainite.) - answerCurve C
- Crosses the 100% border and quenches from there
In this unary phase diagram, which point(s) violate(s) the Gibbs phase rule? -
answerPoint C
- At point C, 4 phases are in equilibrium: Solid1, Solid2, Solid3, and Solid4.
True/False: On a standard temperature-pressure UNARY phase diagram, it is possible
to have AREAS of the phase diagram that include 2 phases in equilibrium with one
another. - answerFalse
- This is unary, not binary
Shown below is the pressure vs. temperature unary phase diagram for SiO2. How many
solid polymorphs of SiO2 are shown in this phase diagram? - answer6 polymorphs
Use the the unary phase diagram for SiO2 shown here to solve this question. Assume
the system is in the Coesite phase at 2500 °C and 7 GPa of pressure (as labelled in the
image). Starting from these conditions, which of the following processes would melt the
