9. Typical microscopic images of spheroidite, lower bainite and tempered martensite of an iron-carbon alloy are represented in the following images; 9.a) Briefly describe the microstructural difference between spheroidite and tempered martensite. 9.b) Explain why tempered martensite is much harder and stronger. 9.c) Briefly describe the microstructural difference between lower bainite and tempered martensite. Ferrite Cementite |05 μη lower bainite - carbides 0.5 μπ tempred martensite - carbides in multiple directions 60 μη oriented in the same direction

9. Typical microscopic images of spheroidite, lower bainite and tempered martensite of an iron-carbon alloy are represented in the following images; 9.a) Briefly describe the microstructural difference between spheroidite and tempered martensite. 9.b) Explain why tempered martensite is much harder and stronger. 9.c) Briefly describe the microstructural difference between lower bainite and tempered martensite. Ferrite Cementite |05 μη lower bainite - carbides 0.5 μπ tempred martensite - carbides in multiple directions 60 μη oriented in the same direction

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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1. Why does the tensile strength of steel, which contains only austenite at room temperature, differ fromsteel that shows only pearlite in its microstructure? Give two important reasons for the difference. 2. What general prerequ_isites exist for the formation of martensite in steel? 3. What is an isothermal transformation of a material in the solid state condition? 4. Draw a typical isothermal transformation diagram for plain .carbon eutectoid steel and indicate thevarious decomposition products expected by simple diagrammatic drawing.
Draw the iron-Fe3C phase diagram. Consider high carbon steel alloy.(min carbon content 0.9C%) a) It is cooled slowly from a temperature within austenite phase to room temperature. Show a) microstructure at 730°C , b) microstructure at 715°C and c) microstructure at room temperature , d) Which phases is seen at room temperature? Pearlite+ proeutectoid ferrite or Pearlite+ proeutectoid cementite. e) What do you say about mechanical properties of this alloy, depending on this microstructure at room temperature?
1) Draw the iron-Fe;C phase diagram. Consider 0.25 and 1.1 wt% C steel alloy. It is cooled slowly from atemperature within austenite phase to room temperature. Show a) microstructure at 1000 °C b) microstructure at 730°C c) microstructure at 715°C and d) microstructure at room temperature e) What do you say about mechanical properties of these alloys, depending on their microstructure at room temperature?
HOME WORK Calculate the amounts of solid phases of ferrite and cementite present in pearlite. y+ FegC a + Fe;C 6.70 0.022 0.76 Composition (wt % C) Temperature
The following questions are based on a high carbon steel with a composition of 1,5% C and 98,5% Fe. Please refer to the Fe-Fe3C binary phase diagram in Callister and Rethwhich 1) a Name the phases present and calculate the amounts of these phases just above the eutectoid temperature b, Give the amount of austenite present at 1100°C. c. Give the amount of pro-eutectoid ferrite just above the eutectoid temperature. d. With equilibrium cooling just below the eutectoid temperature calculate the total ferrite. e. Why must the samples be quenched rapidly to obtain high hardness?
Question 2: For the given Fe-C phase duagram (a) Compute the mass fractions of a ferrite and cementite in pearlite. (b) Compute the mass fraction of eutectoid ferrite in an iron-carbon alloy that contains 0.43 wt% C. (c) The mass fractions of total ferrite and total cementite in an iron-carbon alloy are 0.88 and 0.12, respectively. Is this a hypoeutectoid or hypereutectoid alloy? Why? Temperature (°C) 1600 1400 1200 1000 800 600 400 1538°C (Fe) 912°C M+R -1493°C 1394°C 7. Austenite 0.76 0.022 a, Ferrite y+L 2 2.14 Composition (at% C) 15 10 1147°C a + FezC L 3 Composition (wt% C) 4.30 Y+Fe3C 727°C 20 Cementite (Fe3C). 25 2500 2000 1500 1000 6.70 Temperature (°F)
11.15) Make a copy of the isothermal transforma- tion diagram for an iron-carbon alloy of eutectoid composition (Figure 11.14) and then sketch and label on this diagram time- temperature paths to produce the following microstructures: (a) 100% coarse pearlite. (b) 100% tempered martensite. (c) 50% coarse pearlite, 25% bainite, and pearl- 25% martensite.
Use the copper silver phase diagram below. 100g of a 40 wt% Cu 60 wt% Ag alloy is made and cooled from liquid form. a. At what temperature does the solid phase start to appear? b. What phases exist at 780°C? c. What are the compositions (Cu and Ag%) of the phases in question b? d. What are the weights (in g) of Cu in the solid phase and liquid phase in question b?
1.9 kg of austenite containing 1.50 Wt% C is cooled from 1200 degrees C to a temperature just below the eutectoid line. 1. What is the proeutectoid phase? 2. How many kilograms each of total ferrite and comentite form? 3. How many kilograms each of pearlite and the proeutectoid phase form?
Question 7: The illustration shows the iron-carbon phase diagram. 1600 1400 1200 1000 800 600 400 1538°C 0 (Fe) 1493°C 1394°C 912°C 7. Austenite 0.76 0.022 a, Ferrite Y+L 2.14 Composition (at%C) 15 10 1147 C a+FezC Y+FeyC 4 3 Composition (wt% C) 727 C Cementite (FeyC). 2500 2000 1500 1000 6.70 Temperature (°F) e) Describe the changes in phase compositions of a carbon steel with a carbon content of 1 % (weight-%) from 1500°C down to 727°C with the help of the attached phase diagram and appropriate equations/reactions.
4b) Figure 6 shows the Fe-Fe3C phase diagram. Evaluate (i) the temperature at which austenite first begins to transform on cooling; (ii) the primary microconstituent that forms; (iii) the composition and amount of each phase present at 728°C; (iv) the composition and amount of each phase present at 726°C; (v) Sketch the evolution of the microstructures of hypereutectoid steels with 1.1 wt% of carbon during the cooling in relationship to Fe-Fe3C phase diagram shown at 900°C, 800°C and 500°C, respectively.
A binary alloy having 28 wt% Cu and balance Ag solidifies at 779°C. The solid consists of two phases a and B. Phase a has 9% Cu whereas phase ß has 8 % Ag at 779°C. At room temperature these are pure Ag and Cu respectively Sketch the phase diagram. Label all phases and temperatures. The melting points of copper and silver are 1083 and 9610 respectively s Pà) Estimate the amount of a and B in the above alloy at 779°C and at room temperature.) b) Calculate the mass fraction of phases for 40% Cu alloy at 300 °C and TR c) What is the composition of the alloys in (b)