e45_hw_7 - E45 HW 07 Due October 22, 2010 References: J.F....

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E45 HW 07 Due October 22, 2010 References: J.F. Shackelford, Introduction to Materials Science for Engineers, 6 th Edition, Prentice Hall, New Jersey (2005) Problem 1 10.3 Although Section 10.1 concentrates on crystal nucleation and growth from a liquid, similar kinetics laws apply to solid-state transformations. For example, Eq. 10.1 can be used to describe the rate of β precipitation upon cooling supersaturated α phase in 10 % wt Sn-90 wt % Pb alloy. Given precipitation rates of 3.77 x 10 3 s -1 and 1.40 x 10 3 s -1 at 20 °C and 0 °C, respectively, calculate the activation energy for this process. SOLUTION Ġ = C e (-Q/RT) (Source: Shackelford, Eq. 10.1, p. 359) R = 8.314 J/(mol K) T = 273 K, 293 K Ġ 293K (growth rate at 20 °C) = 3.77 x 10 3 s -1 Ġ 273K (growth rate at 0 °C) = 1.40 x 10 3 s -1 We can find Q by writing separate eqns for 20 °C and 0 °C and setting them equal to each other. Ġ
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This note was uploaded on 11/19/2010 for the course E 45 taught by Professor Gronsky during the Fall '08 term at University of California, Berkeley.

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e45_hw_7 - E45 HW 07 Due October 22, 2010 References: J.F....

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