Homework2

Homework2 - Fall 2011 Due: 09/19/2011 Homework 2 1. What...

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Unformatted text preview: Fall 2011 Due: 09/19/2011 Homework 2 1. What are the two forms of solid solutions we discussed and how are they formed? (2’) 2. What is a stoichiometric intermetallic compound, and how would it appear in a temperature­composition phase diagram? How would a nonstoichiometric intermetallic compound appear? (3’) 3. Describe the relative ability of iron to dissolve carbon in solution when in the form of austenite (the elevated temperature phase) and when in the form of ferrite at room temperature (2’) 4. At 0.77% Carbon, austenite transforms to pearlite (mixture of two phases: ferrite and cementite: Fe3C). When it slowly cools from 727C0 below 725C0, what is the composition of the two phases in pearlite, and in what ratio are they present? (Hint: Use Inverse Lever Rule to find the ratio of compositions) (3’). 5. For an alloy containing 50% Cu and 50% Ni, calculate the amounts of solid S and liquid L presents at 1300C. Show that the total nickel content in the solid and liquid phases adds up to 50%. When this alloy is cooled gradually from 1500oC comment on whether the first piece of solid that forms has a composition which is rich in Cu or rich in Ni? Why? (5’) (Note: Rich in Ni implies Ni% is greater than Cu% and vice versa) 1 Fall 2011 Due: 09/19/2011 6. Calculate the relative proportions of phases in Cu­Ag alloy of eutectic composition, just below the eutectic temperature. During the cooling of an Alloy (Cu 80% Ag 20%) from 1100C to 600C, describe the phase transitions during the cooling (Hint: There are two critical transitions).(3’) 7. Very briefly discuss how the cooling curves for different compositions are useful for developing the phase diagrams. (Hint: Refer to the cooling curves for different solutions of salt and water from Chapter 4 or Lecture notes for Chapter 4)(2’) 2 ...
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