Dotted vs Regular Lines on Iron-Carbon Alloy Diagrams

In summary, the difference between the dotted lines and the regular lines on the iron-carbon alloy diagrams is that the dashed lines represent eutectics and eutectoids, while the other lines represent phase boundaries. The dashed lines are used to distinguish from other lines and indicate the 50/50 boundary between austenite and pearlite or bainite. There are also two horizontal dashed lines that represent the 50% and 90% Martensitic transformation. This transformation requires rapid quenching from a high temperature to the appropriate temperature indicated by the horizontal lines.
  • #1
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What's the difference between the dotted lines and the regular lines on the iron-carbon alloy diagrams?
 
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  • #3
Sorry! I made a mistake. It's called the continuous cooling transformation diagram of iron-carbon alloy of euctectoid composition... I saw that in a book I'm reading called "Fundamentals of Materials Science and Engineering (2nd Edition)" by William D. Callister, Jr., and the diagrams are on page 444 and pg. 445...
 
  • #4
Using W. D. Callister's, "Material Science and Engineering, An Introduction", 6th Edition, I indentified an isothermal transformation diagram for iron-carbon of eutectoid composition. A = austenite (FCC), B = bainite, P = pearlite, and M = Martenite (BCT).

I think the dashed lines are simply used to distinguish from other lines. There is one curvy dashed line between the fully A and fully P or B phases, and the dashed line simply shows the 50/50 boundary between A/P or A/B.

Then there are two horizontal dashed lines which represent the 50% Martensitic transformation at 165°C and 90% M-transformation at ~130°C. The transformation from A to M requires starting with the heat at or above 727°C and rapidly quenching to the appropriate temperature (one of the horizontal lines).
 
  • #5
ok, thank you very much!
 

FAQ: Dotted vs Regular Lines on Iron-Carbon Alloy Diagrams

What is an iron-carbon alloy diagram?

An iron-carbon alloy diagram, also known as an iron-carbon phase diagram, is a graphical representation of the phases that form in the iron-carbon system at different compositions and temperatures. It is used to understand the relationship between the microstructure and properties of iron-carbon alloys.

What are the different phases shown on an iron-carbon alloy diagram?

The phases shown on an iron-carbon alloy diagram include ferrite, austenite, cementite, and graphite. Ferrite is a solid solution of carbon in iron with a body-centered cubic structure. Austenite is a solid solution of carbon in iron with a face-centered cubic structure. Cementite is a compound of iron and carbon with a fixed ratio of 6.67% carbon. Graphite is a non-metallic form of carbon that can form in iron-carbon alloys with high carbon content.

How is an iron-carbon alloy diagram used in materials science?

An iron-carbon alloy diagram is used in materials science to predict the microstructure and properties of iron-carbon alloys at different compositions and temperatures. It is also used to determine the appropriate heat treatment processes for producing desired microstructures and properties in iron-carbon alloys.

What is the eutectic point on an iron-carbon alloy diagram?

The eutectic point on an iron-carbon alloy diagram is the point at which the liquid phase transforms into two solid phases, ferrite and cementite, at a specific temperature and composition. This point marks the lowest melting point of an iron-carbon alloy and is important in understanding the solidification behavior of iron-carbon alloys.

How does the carbon content affect the microstructure of iron-carbon alloys?

The carbon content has a significant impact on the microstructure and properties of iron-carbon alloys. As the carbon content increases, the amount of austenite phase also increases, resulting in a harder and more brittle alloy. However, too much carbon can lead to the formation of graphite, which weakens the alloy. The carbon content also affects the eutectic point and the type of iron-carbon alloy (cast iron, steel, or wrought iron) that will form.

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