6. Describe each of the following crystal structure imperfections: a) substitutional atom; b) interstitial atom; c) vacancy. 7. At equilibrium, what is the maximum amount of carbon that can dissolve in pure iron at 600°C (by wt%). If the carbon content exceeds this maximum value, briefly describe the microstructure of the resulting alloy. 8. Give an example of a stress concentration in a metal part. 9. How would you expect the mechanical properties of a metal with an FCC structure to differ from one with a BCC structure? Why? 10. What is a slip system and how is it different than a slip plane?

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Is it possible to have a copper-nickel alloy that, at equilibrium, consists of a liquid phase of composition 20 wt% Ni-80 wt% Cu and also an a phase of composition 37 wt% Ni-63 wt% Cu? If so, what will be the approximate temperature of the alloy? If this is not possible, explain why. Temperature (°C) 1600 1500 1400 1300 1200 1100 1000 0 1085°C (Cu) 20 Liquid Liquidus line L B 40 a+L a A 60 Composition (wt% Ni) (a) 1455°C Solidus line 80 2800 2600 2400 2200 2000 100 (Ni) Temperature (°F) Temperature (°C) 1300 1200 20 Liquid Tie line. a + Liquid a 1 KR I 1 1 B ↑ Co a + Liquid -S 30 CL Composition (wt% Ni) (b) 40 1 Ca a 50

A metal has a certain fraction f = 105 of vacancies at the atomic level at finite temperatures. If the activation energy for vacancy formation was increased by 50%, what would be the new vacancy concentration? Select one: a. 7.43E-10 b. 6.22 E-5 C. 1.24E-6 O d. 3.16E-8 e. 5.48E-4