Need help in hurry about phase transformations

In summary: In this case, the interfacial energy between the two phases may be lower than the elastic energy associated with the deformation of the matrix phase.In summary, facing is a phenomenon associated with crystalline materials undergoing phase transformation. The general energies associated with a small precipitate of phase β in a matrix phase α include strain energy, interfacial energy, and elastic energy. As a precipitate grows, it loses coherency due to increased elastic strain energy. The stable shape of a precipitate can indicate the relative interfacial energy between phases.
  • #1
LynnCGL
1
0
I'm studying in a class about phase transformations, and have a couple of questions needing answers/clarification:

N0.1

A metallic sample can show faceing when heated, but a plastic sample does not because_______?

NO.2

a)What are the general energies associated with a small precipitate of phase β inside a matrix phase α.(Assume spherical precipitates initially)

b)Often, a small precipitate starts as a coherent one,then is loses coherency as it grows beyond a certain critical radius(r).Explain this observation briefly and illustrate with a schematic plot.

c)If the stable shape of the precipitate tends to become plate or disc shaped (e.g.figure 2),what can you comment about the interfacial energies involved?

and the last questin also showed on the pic.

Need help,thank you very much
 

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  • #2
.A1. A plastic sample does not show facing when heated because plastics are not crystalline materials, and facing is a phenomenon associated with crystalline materials as they undergo phase transformation.A2a. The general energies associated with a small precipitate of phase β inside a matrix phase α are the sum of the strain energy associated with the deformation of the matrix phase, the interfacial energy between the two phases, and the elastic energy stored in the precipitate.A2b. As a precipitate grows beyond a certain critical radius (r), it loses coherency due to increased elastic strain energy. This can be illustrated with a schematic plot showing the change in energy as a function of precipitate size.A2c. If the stable shape of the precipitate tends to become plate or disc shaped, this indicates that the interfacial energy between the two phases is relatively low, which is necessary for the formation of larger precipitates.
 

FAQ: Need help in hurry about phase transformations

1. What are phase transformations?

Phase transformations are changes in the physical structure of a material, resulting in a transition from one phase to another. This can include changes in the atomic arrangement, crystal structure, or chemical composition of a material.

2. Why is understanding phase transformations important?

Understanding phase transformations is important in various fields of science and engineering, as it can affect the properties and behavior of materials. This knowledge can be used to design and improve materials for specific applications, such as in the development of new alloys or in controlling the microstructure of materials for better performance.

3. What factors influence phase transformations?

Phase transformations can be influenced by various factors, including temperature, pressure, composition, and external stimuli such as mechanical stress or electromagnetic fields. These factors can affect the energy state of the material and its ability to undergo a phase transformation.

4. How do scientists study phase transformations?

Scientists use various techniques to study phase transformations, including microscopy, spectroscopy, and diffraction methods. These techniques allow them to observe and analyze the changes in the material's structure and properties during a phase transformation.

5. Can phase transformations be controlled?

Yes, phase transformations can be controlled through the manipulation of the influencing factors such as temperature, pressure, and composition. This allows scientists and engineers to tailor the properties of materials to meet specific needs and applications.

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