The nature of the final microstructure (in terms of microconstituents present and approximate percentages) of an...

 

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The nature of the final microstructure (in terms of microconstituents present and approximate percentages) of an unknown Fe-C alloy steel specimen is characterized and found as: 18.60% ferrite, 40.70% perlite, 20.35 % bainite and 20.35 % martensite. The elemental analysis shows that the specimen contains chromium, nickel and molybdenum, and it should be 43XX steel. As a materials science engineer, use the binary Fe-C phase diagram and the TTT diagram, given, to answer the following questions: a) If the ferrite formed within this alloy is the maximum amount possible i. What is the amount (wt% C) of carbon within this Fe-C alloy (43??)? ii. Complete the missing part of the TTT diagram based on your engineering judgement. b) Using the TTT diagram you completed reverse-engineer the heat treatment (time-temperature) procedure (Draw on the TTT diagram) for this specimen? c) Specify the nature of the final microstructure for the following heat treatment procedure for the same alloy: Heat up to 950 °C and wait long enough to equilibrate, rapidly cool to 620 °C, hold for 1000 s, then rapidly cool to 400 °C, hold for 100 s and then quench to room temperature. d) To be able to form 100% martensitic steel what should be the minimum cooling rate for this 43XX alloy? e) You should be familiar with the 10XX type Fe-C phase diagram so comparing it with the 43XX type phase diagram given comment on the effects (you recognize on both the phase and TTT diagrams) of the alloying (Cr, Ni and Mo) elements. The nature of the final microstructure (in terms of microconstituents present and approximate percentages) of an unknown Fe-C alloy steel specimen is characterized and found as: 18.60% ferrite, 40.70% perlite, 20.35 % bainite and 20.35 % martensite. The elemental analysis shows that the specimen contains chromium, nickel and molybdenum, and it should be 43XX steel. As a materials science engineer, use the binary Fe-C phase diagram and the TTT diagram, given, to answer the following questions: a) If the ferrite formed within this alloy is the maximum amount possible i. What is the amount (wt% C) of carbon within this Fe-C alloy (43??)? ii. Complete the missing part of the TTT diagram based on your engineering judgement. b) Using the TTT diagram you completed reverse-engineer the heat treatment (time-temperature) procedure (Draw on the TTT diagram) for this specimen? c) Specify the nature of the final microstructure for the following heat treatment procedure for the same alloy: Heat up to 950 °C and wait long enough to equilibrate, rapidly cool to 620 °C, hold for 1000 s, then rapidly cool to 400 °C, hold for 100 s and then quench to room temperature. d) To be able to form 100% martensitic steel what should be the minimum cooling rate for this 43XX alloy? e) You should be familiar with the 10XX type Fe-C phase diagram so comparing it with the 43XX type phase diagram given comment on the effects (you recognize on both the phase and TTT diagrams) of the alloying (Cr, Ni and Mo) elements.

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a If the ferrite formed within this alloy is the maximum amount possible i To determine the amount of carbon within the FeC alloy 43XX we can use the lever rule The lever rule states that the weight f... View the full answer