There is no compositional change during phase transformations e.g the melting of a pure metal.
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Describe a incongruent transformation
At least one of the phases would experience com positional change. e.g eutectic, peritectic reactions - the melting of an alloy
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What is the 'liquidus surface'?
A plot of the temperatures above which a homogeneous liquid forms for any given overall composition.
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What is the 'solidus surface'?
A plot of the temperatures below which homogeneous solid phase forms for any given overall system.
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Describe the Gibbs triangle
Pure components are represented by each corner and it is used o determine the compositions.
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How can composition be determined using the Gibbs triangle?
1) Draw line passing through X and parallel to each of the sides.2)Where the lines intersect the side AB tells the concentration of component B in X.
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Give the expression for degree of freedom and the maximum F for this system?
F = 4-P; F_max = 3 ] temperature, and 2 concentrations are needed to completely define the system.
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What is an 'Isothermal plot'?
A 'horizontal' section of a ternary phase diagram obtained by cutting through the space diagram at a specified temperature.
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How can the composition of two phases on the two phase region be determined?
1) Draw tie -line through X to intersect the phase boundaries at Y and Z.2)Composition of liquid phase = location of point Y within Gibbs triangle. --> Assumes that Z has already been determined experimentally
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Describe the ternary eutectic reaction
A liquid phase transforms at once into three solid phases during cooling (made up of 3 binary eutectic systems).
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What does an isothermal plot at a temperature below the eutectic temperature show?
Shows phases present at a particular temperature It is used to predict the phases, their amounts and composition at a particular temperature.
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Other cards in this set
Card 2
Front
Describe a incongruent transformation
Back
At least one of the phases would experience com positional change. e.g eutectic, peritectic reactions - the melting of an alloy
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