What Microstructure Results from Complex Cooling of 1.13% C Steel?

[yecko]

Homework Statement

Q10.20 Using the isothermal transformation diagram for a 1.13 wt% C steel alloy (Figure 10.39), determine the final microstructure (in terms of just the microconstituents present) of a small specimen that has been subjected to the following time–temperature treatments. In each case assume that the specimen begins at 920 degree celsius and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure.

(e) Rapidly cool to 650 degree celsius, hold at this temperature for 3 s, rapidly cool to 398 degree celsius, hold for 25 s, then quench to room temperature.Answer: Cementite, medium pearlite, bainite, and martensite

Homework Equations

[/B]
the existence of “pearlite, bainite, and martensite” is because the curve went through the region of “A+P”, “A+B” and “M”.

The Attempt at a Solution

(Same with “relevant equation” session)why would there be cementite?

The curve didn’t went through any other region, and there isn’t even a label indicating cementite (though there is C for proeutectoid cementite…)Thank you very much!

 

[Baluncore]

Cementite in any form of micro-structure is still cementite.
This may be helpful. https://www.iitk.ac.in/tkic/slides/Microstructure/L-4.pdf