# HW9-new - and 0.09 respectively, specify whether the alloy...

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ME311 MATERIALS ENGINEERING SPRING 2011 HOMEWORK #9 DUE DATE: April 8, before class PROBLEM 1: The microstructure of an iron-carbon alloy consists of pro-eutectoid ferrite and pearlite where the mass fractions of these two phases are 0.286 and 0.714, respectively. Determine the concentration of carbon in this alloy. PROBLEM 2: For an iron-carbon alloy of composition 5 wt% C, draw sketches of the microstructure that would be observed for conditions of very slow cooling at the following temperatures: 1175 C, 1145 C and 700 C. Label the phases and indicate their compositions. PROBLEM 3: In the case of a hypoeutectoid Fe-C alloy, primary ferrite forms first at the austenite grain boundaries during cooling before forming within the austenite grains. Can you explain this phenomenon? PROBLEM 4: What is the carbon concentration of an iron-carbon alloy for which the fraction of total ferrite is 0.94? PROBLEM 5: Assuming the mass fractions of ferrite and cementite for an iron-carbon alloy are 0.91

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Unformatted text preview: and 0.09 respectively, specify whether the alloy is hypoeutectoid or hypereutectoid? PROBLEM 6: Below is shown the isothermal transformation diagram for a eutectoid iron-carbon alloy. Indicate the time-temperature paths that will yield (a) 100% coarse pearlite; (b) 50% martensite and 50% austenite; and (c) 50% coarse pearlite, 25% bainite, and 25% martensite. PROBLEM 7: Below is shown a continuous cooling transformation diagram for a 0.35 wt% C iron carbon alloy. Sketch on the diagram continuous cooling paths that will produce (a) fine pearlite and proeutectoid ferrite; (b) martensite; (c) martensite and proeutectoid ferrite; (d) coarse pearlite and proeutectoid ferrite; and (e) martensite, fine pearlite, and proeutectoid ferrite. PROBLEM 8: Explain why martensite is hard and brittle and why its hardness decreases with tempering time and with increasing temperature?...
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## This note was uploaded on 09/04/2011 for the course ME 311 taught by Professor Meyers during the Spring '08 term at University of Texas at Austin.

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HW9-new - and 0.09 respectively, specify whether the alloy...

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