Suppose that a steel of eutectoid composition is cooled to 675°C (1250°F) from 760°C (1400°F)in less than 0.5 s and held at this temperature.(a) How long will it take for the austenite-topearlite reaction to go to 50% completion? To 100%completion?(b) Estimate the hardness of the alloy that has completely transformed to pearlite.

(a) How long will it take for the austenite-to-pearlite reaction to go to 50% completion? To 100%…

Answered: Suppose that a steel of eutectoid…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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A 0.25% C hypoeutectoid plain-carbon steel is slowly cooled from 950°C to a temperature just slightly below 723°C.(a) Calculate the weight percent proeutectoid ferrite in the steel.(b) Calculate the weight percent eutectoid ferrite and weight percent eutectoid cementite in the steel.
For a 64 wt% Zn-36 wt% Cu alloy, make schematic sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures: 900°C (1650 F), 820°C (1510 F), 750°C (1380°F), and 600°C (1100 F). Label all phases and indicate their approximate compositions.
Use the TTT diagram for O1 Tool steel provided above to estimate the amounts ofpearlite and martensite formed in the quenched heat-treated samples.
Problem 4 A 50 wt% Ni-50 wt% Cu alloy is slowly cooled from 1400°C (2550°F) to 1200°C (2190°F). (a) At what temperature does the first solid phase form? (b) What is the composition of this solid phase? (c) At what temperature does the liquid solidify? (d) What is the composition of this last remaining liquid phase?
If a eutectoid steel sample is heated to 800°C and then quenched in a cold-water bath then what would be the possible microstructure? Draw the microstructure and label it.
3.The TTT diagram of a plain carbon steel is given in Fig. 1. Identify whether this steel is a hypoeutectoid, eutectoid or hypereutectoid steel. Explain why the transformation happens slowly at 850°C as well as at 300°C. Determine the microstructures expected in this type of steel after the following heat treatment processes. a) Austenize at 900°C, quench to 400°C and hold for 1000 s and quench to 25°C. b) Austenize at 900°C, quench to 25°C. c) Austenize at 900°C, quench to 675°C and hold for 1 s, quench to 400°C and hold for 900 s and slowly cool to 25°C. 900 Acm Cs 800 A1 FezC + Y 33 Fe3C + pearlite 45 700 Ps 600 ++ Fe3C + pearlite Y+ bainite Bs 500 46 Bainite 400 Yu Bf 300 57 Ms 200 60 Mf Y+ martensite 100 62 Martensite 102 65 103 104 105 106 0.1 1 10 Time (s) Fig. 1 Temperature (°C) Rockwell C hardness
A 80%Sn-20%Pb alloy is melted fully at 300°C and then slowly cooled down to 182°C. Sketch the microstructures at 300°C, 200°C, and 182°C, respectively. Label all phases and indicate their approximate compositions. Also, determine the follows for this alloy at 182°C. (1) The weight fractions of α and β phases.(2) The weight fractions of primary β and eutectic structure.(3) The weight fraction of eutectic β .
For a 70-30 Zn-Cu alloy, what would the percent of each phase be at 800°C and 500°C?
For a 50-50 Mg-Pb alloy, what would the percent of each phase be at 500°C, 300°C and 100°C?
Heating 1 pound of a common low carbon steel with 0.50 wt% C content to 1000oC and then slowly cooling it down to room temperature. The iron phase diagram is shown below. (a) What is the eutectic temperature, eutectic composition, and eutectic reaction? (b) What is the eutectoid temperature, eutectoid composition, and eutectoid reaction? (c) At 728oC, what phases do you have and what is the mass of each phase? (d) At room temperature, what phases do you have and what is the mass of each phase?
(b) Figure Q4 (b) displays the time-temperature cooling paths for a 1080 steel on an isothermal transformation diagram. Start with the steels in the austenitic condition at time = 0 and 850°C. Interpret the final microstructures that will be obtained for paths (i, ii and iii) shown in the figure. 700 600 500 400 300 (iii) Ms 200 (i) (ii) Mf Figure Q4 (b)
By using the time-temperature-transformation (TTT) diagram for a steel of eutectoid composition (Fe-C alloy with 0.77 wt% carbon) given below, answer the following questions: Sketch the cooling path(s) on the TTT diagram provided below in answering each question and label them clearly. a) What is meant by the so-called critical cooling rate (CCR)? What happens if this eutectoid steel is quenched from 1000 oC at a cooling rate that is faster than the critical cooling rate? Trace the cooling path on the diagram. What is the crystal structure before and after the quenching? b) What are the effects of alloying elements on the position of the boundaries on a TTT diagram? What are the engineering implications of such effects on the boundaries on a TTT diagram? Concisely elaborate on your answer. c) A steel that is comprised of 25% Pearlite, 37.5% Bainite and 37.5% Martensite is needed for a special application. Design a heat treatment by which such a steel microstructure and be created.…

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