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Unformatted text preview: ME311 MATERIALS ENGINEERING SPRING 2011 HOMEWORK #10 DUE DATE: April 22, before class PROBLEM 1: For a phase transformation that obeys the Avrami equation, the parameter n is known to have a value of 1.7. If, after 100 s, the reaction is 50% complete, how long (total time) will it take the transformation to go to 99% completion? PROBLEM 2: It is known that the kinetics of transformation for some alloy obey the Avrami equation and the value of n in the exponential is 5. If at some temperature, the fraction transformed is 0.3 after 100 min, determine the rate of transformation at this temperature? PROBLEM 3: In aged aluminum alloys with a composition of 96at% Al and 4at% Ag, γ ’ precipitates form on the Al-matrix as thin discs (radius r and thickness 0.1 r). The surface energy of flat interfaces is 250 mJ/m 2 , while the surface energy of the curved interface is 500 mJ/ m 2 . Assume the lattice parameter of the Al-matrix to be 2.450 Å and the lattice parameter of the γ ’ precipitates to be 2.502 Å. In addition, assume ΔGv= 1x10’ precipitates to be 2....
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- Spring '08
- Tensile strength, lattice parameter, Avrami equation, ME311 MATERIALS ENGINEERING