Dotted vs Regular Lines on Iron-Carbon Alloy Diagrams

[asdf1]

What's the difference between the dotted lines and the regular lines on the iron-carbon alloy diagrams?

 

[Astronuc]

Is this the diagram? -
http://en.wikipedia.org/wiki/Image:Phase_diag_iron_carbon.PNG

http://en.wikipedia.org/wiki/Eutectic

The dashed lines coincide with eutectics and eutectoids. The other lines represent phase boundaries.

 

[asdf1]

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...

 

[Astronuc]

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).

 

[asdf1]

ok, thank you very much!