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MTL200 > Chapter 9 - Phase Diagrams > Flashcards

Chapter 9 - Phase Diagrams Flashcards

1
Q

What is a component?

A

Any metal that is part of an alloy

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2
Q

What is a system?

A

Either a specific alloy or series of alloys

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3
Q

What is a solubility limit?

A

The maximum concentration of solutes that may dissolve in a solvent to form a solid solution

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4
Q

What is a phase?

A

A homogenous portion of a system that has uniform physical and chemical characteristics

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5
Q

What is free energy?

A

A function of a systems internal energy and entropy

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6
Q

When is a system at equilibrium?

A

The free energy is at a minimum

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7
Q

What is phase equilibrium?

A

When an equilibrium is referred to in a multiphase system

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8
Q

What is a non-equilibrium state?

A

Equilibrium is not approached due to the rate of approaching equilibrium being very slow

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9
Q

What is a phase/equilibrium diagram?

A

Depicts the different phases a system can have, separated by lines

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10
Q

What is a binary phase diagram?

A

Depicts the phases of a two component system at various temperatures and compositions

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11
Q

What type of system is the copper-nickel system?

A

Binary Isomorphous

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12
Q

What is an isomorphous system?

A

There is complete liquid and solid solubility

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13
Q

What phases are included in binary isomorphous systems?

A

Alpha (a), Liquid (L), and both (a + L)

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14
Q

What information does a phase diagram provide?

A

The phases, compositions at said phases, and the percentages of said phases

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15
Q

What is the solidus line?

A

Separates the solid/liquid phase from the pure liquid phase

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16
Q

What is the liquidus line?

A

Separates the L and a + L phases

17
Q

How is a composition determined when the point chosen lies in a two phase region?

A

By using a tie line and then using linear interpolation
WL = (Ca - C0)/(Ca - CL)
Wa = (C0 - CL)/(Ca - CL)

Ca = concentration of alpha phase at tie line
CL = concentration of liquid phase at tie line
C0 = concentration of component at point
W = weight fraction

18
Q

What happens to the microstructure at an equilibrium cooling?

A

The change in temperature is extremely slow, so the phase change occurs smoothly

19
Q

What happens to the microstructure at a non-equilibrium cooling?

A

Compositional readjustments are necessary

20
Q

What is a binary eutectic phase diagram?

A

Contains 3 pure phases, a, B, and L, and mixed phases, a + L, a + B, B + L

21
Q

What is the solvus line?

A

The line that separates a pure solid phase from the mixed solid phase (a + B)

22
Q

What is a eutectic reaction?

A

The reaction occurs at point where the metal is easily melted

23
Q

What is the eutectic point?

A

The point where the liquidus lines for both pure metals meet on the eutectic isotherm

24
Q

How is a eutectic reaction defined?

A

L(CE) = a(CaE) + B(CBE)

25
Q

What is the difference between eutectic and primary a’s or B’s

A

Primaries are formed before crossing the eutectic isotherm

26
Q

What is the eutectic isotherm?

A

The horizontal line separating the a + B phase from the phases that include L

27
Q

What is a terminal solid solution?

A

A solution with only solid phases, found at the extremes

28
Q

What is an intermediate solid solution?

A

Solid solutions found at spots other than the composition extremes

Not at 100% of each metal in the alloy

29
Q

What is a eutectoid reaction?

A

Consisting of 3 solid phases, delta (d) = gamma (y) + epsilon (e)

30
Q

What is a peritectic reaction?

A

d + L = e

31
Q

What does Gibbs’ Phase Rule describe?

A

It describes the number of phases present within a system in terms of the number of external variables, components, and non-compositional variables
P + F = C + N

32
Q

What are some intermediate phases of the iron-carbon alloy?

A

Iron carbide (cementite), gamma-iron (austentite), delta ferrite, alpha ferrite, pearlite,

33
Q

Which phase is the eutectic structure?

A

a + B

MTL200 (8 decks)

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