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

AI Thread Summary
The discussion centers on determining the final microstructure of a 1.13 wt% C steel alloy after specific cooling treatments. The treatments involve rapid cooling to 650 degrees Celsius, followed by a hold and further cooling, resulting in the presence of cementite, medium pearlite, bainite, and martensite. Participants question the inclusion of cementite in the microstructure, noting that the cooling curve does not explicitly indicate its formation. Clarifications emphasize that cementite can exist in various forms within the microstructure, regardless of the cooling path taken. The conversation highlights the complexity of phase transformations in steel alloys during cooling processes.
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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

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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!
 

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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
 
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