iron-carbon alloy diagram

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:P...ron_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 continous 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!