Use the following TTT diagram to answer question 11-13 Cooling curve A produces

Question

Use the following TTT diagram to answer question 11-13 Cooling curve A produces in an eutectoid steel Martensite Bainite Pearlite Spherodite phase formed through cooling curve B in an eutectoid steel is Very soft and ductile Coarse pearlite Very hard but brittle None of the above Draw cooling curve on the TTT diagram that diagram that corresponds to Austempering heat treatment for eutectoid alloy. Given the microstructures of a low carbon steel, the phases shown are identified as (a) ia Pearlite and (b) is Bainite (a) is austenite and (b) is Pearlite (a) is Martensite and (b) is Pearlite (a) is Bainite and (b) is Pearlite

Explanation / Answer

21. In a eutectoid steel perlite is formed when austinite cools below at a temperature of below 727 degree celsius. So in the graph also below 727 degree celsius tha cooling curve A represents Perlite.

22.Phase formed through cooling curve B in euctectoid steel will be Martensite which is formed by quenching or austenite so fast such carbon do not get enough time to diffuse out of the strurcture of the crystals and form cementaite. As a result the Austenite which is face centered transformed to body centered arrangement tetragonal Matensite arrangement that is supersaturated with carbon and so it is very hard but brittle

24. D. the figure A is bainite and Figure B is Pearlite. Bainite forms in steel at temperture of about 250-55) degree celisus and is platy like microstructures whereas Perlite is laminellar like structure and forms below 727degree celsius.

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.